
Class 

Book 

Copyiigfit]^". 



CDPVRIGHT DEPOSIT. 



LABORATORY WORK 

IN 

APPLIED CHEMISTRY 

FOR STUDENTS IN DOMESTIC SCIENCE 



ABRAHAM HENWOOD 

Professor of Chemistry 

FRANK H. GRIFFIN 

Instructor in Chemistry 

DREXEL INSTITUTE 



Published by 

THE INSTITUTE PRESS 

Drexel Institute, Philadelphia 

1912 




Copyright 1912, 
Bii the Authors 



^CI.A327;{71 



I. DETERGENTS AND CHEMICALS EMPLOYED IN 
THE LAUNDRY. 

A. WATER FOR LAUNDRY WORK. 

Natural Waters Are Solutions. 

Principle of the Method. — An accurately measured 
volume of water to be examined is evaporated in a weighed 
vessel. The vessels together with the dry solid residues is 
weighed, the amount of solid residue being determined by sub- 
traction of the two weights. 

Apparatus. — Convex cover (10 cms.) ; 500 c.c. lipped 
beaker, ring stand, wire gauze, Bunsen burner, 100 c.c. graduated 
flask, balance and weights. 

Details of Procedure. — Place the beaker one-tjiird filled 
with water on the wire gauze and heat to boiling. While the 
water in the beaker is being heated, weigh the convex cover to 
the nearest milligram, first having scrupulously cleaned and dried 
it. Measure into the graduated flask 100 c.c. of the water to 
be examined or such a volume as will leave not less than 10 
milligrams of solid residue on evaporation. Place the weighed 
convex cover on top of the beaker containing the boiling water 
and carefully add a portion of the measured volume of water. 
As it evaporates, add more and more, until the whole has been 
evaporated. Continue the evaporation until the residue on the 
cover appears perfectly dry. Cool in a desiccator and weigh 
with the same precision as before. 

Calculation of Result. — Express the result as parts 
per million and as grains per U. S. gallon. Consult works in 
the library or other sources to secure similar data on other 
waters and arrange them in the form of a table. 

Sources of Error. — Aside from mistakes or other inac- 
curacies in weighing or measuring, serious error may creep in 
through the accumulation of dust during the evaporation. This 
may be guarded against by suspending an inverted funnel over 
the cover. 



The Effect of Dilute Solutions of Salts on Soap Solutions. 

Principle of the Method. — Soap solution gives suds when 
shaken with water. The amount of the solution of soap neces- 
sary depends upon the proportion of dissolved salts in tlie 
water. 

Apparatus. — A glass-stoppered bottle (capacity about 200 
to 250 CO.), burette, 100 c.c. pipette. 

Reagents. — Alcoholic soap solution. 10 grams powdered 
Castile soap in 1 liter, ('ilute alcohol (1/3 water) ; appro .ximately 
0.00-4 N solutions of aluminum chloride, ferrous chloride, man- 
ganous sulphate, calcium chloride, magnesium sulphate. 

Details of Procedure. — Measure 100 c.c. of distilled water 
into the glass bottle. Fill the burette with soap solution. Add 
the soap solution 1 c.c. at a time to the contents of the bottle, 
stoppering and shaking after each addition. Continue the addi- 
tion of the soap solution until a suds is obtained, which persists 
for' five minutes. Record the number of c.c. of soap solution 
recjuired. Repeat with each of the salt solutions mentioned. 

Conclusion. — Record the results in a table. 

The Effect of Dilute Solution of Calcium Bicarbonate on Soap 
Solutions. 

Reagents. — Alcoholic soap solution prepared as directed in 
the preceding experiment ; saturated solutions of calcium hy- 
droxide and calcium sulphate. 

Details of Procedure. — Pass carbon dioxide gas through 
25 c.c. of the saturated calcium hydroxide solution until the 
precipitate that forms is entirely dissolved. Dilute to 200 c.c. 
with distilled water. Divide the solution into two equal parts. 
To the first, add soap solution in exactly the same manner as 
directed in the preceding experiment. Record the result. Boil 
the second part until no more CO2 is evolved. Note the result. 
( ?). Restore the volume to 100 c.c. with distilled water and 
again test with soap solution. Repeat the experiment, using a 
solution of calcium sulphate (1 c.c. of the saturated solution 
diluted to 100 c.c. with distilled water). 

Questions.— Write the equations for each step in the above 
experiment. 

What is meant by "Hardness of Water"'? 



Which part of the above experiment illustrates water of 
temporary and which water of permanent hardness? Give rea- 
sons for your answer. 

Determination of the Soap Consuming Power of Water. 

Principle of the Method. — A soap solution is standard- 
ized by titration against an artificial water of known degree of 
hardness. Natural waters are examined as to their soap con- 
suming power by titration with this standard soap solution. 

Apparatus. — A glass-stoppered bottle of 200 to 250 c.c. 
capacity, burette, pipettes (10 c.c. and 100 c.c), 100 c.c. gradu- 
ated cylinder, graduated liter flask. 

Reagents. — Weigh accurately one gram of pure calcite 
(CaCOg). Dissolve in HCl and evaporate to dryness to expel 
the excess of acid. Take up with water, add a drop of ammonia 
and dilute to a liter in the graduated flask. This solution con- 
stitutes a standard hard water 1 c.c. = .001 grams CaCO.; ; soap 
solution used in the previous experiment. 

Details of Procedure. — Place 10 c.c. of the standard hard 
water, measured by a pipette, in the glass stoppered bottle, add 
90 c.c. of distilled water, then soap solution from the burette 3^ 
c.c. at a time, shaking after each addition, until a lather is 
formed, which persists for five minutes. Record the number of 
c.c. used. This gives the approximate amount of soap solution 
equivalent to 10 c.c. of the standard hard water, plus 90 c.c. of 
distilled. Repeat this operation until three results are obtained, 
which do not vary in reading more than ^ c.c. This mean 
reading gives the true value in c.c. of soap solution equivalent 
to 10 c.c. of the standard water, plus 90 c.c. of distilled. Since 
distilled water itself requires some soap solution before a lather 
is obtained, a blank is run in a similar manner to the above on 
100 c.c. of distilled water. By subtracting the mean here ob- 
tained from the mean number of c.c. obtained in the first in- 
stance, the quantity of soap solution equivalent to .01 grams 
CaCOg is obtained. Calculate the value of 1 c.c. of the soap solu- 
tion in terms of CaCO-j. 

With the solution so standardized, determine the soap con- 
suming power of several waters. Place 100 c.c. of the water 
to be examined in the glass stoppered bottle and add standard 
soap solution in exactly the same manner as in the standardiza- 



tion. Read the number of c.c. of soap solution required and 
calculate the hardness of the water. 

Calculation of the Result. — Express the hardness of 
the water in terms of parts of CaCOj per million. 

Multiply the known value of 1 c.c. of soap solution by the 
number of c.c. used, and again multiply by 10 in order to ex- 
press the hardness in parts per million. 

Determination of the Temporary Hardness (Alkalinity) of 
Water. 

Principle of the Methd. — If we assume that all the acid 
consuming substances of the water are calcium and magnesium 
bi-carbonates, the amount of acid used to neutralize the water 
is a measure of the temporary hardness. 

Apparatus. — 1000 c.c. beaker, stirring rod, 100 c.c. pipette, 
burette, 1000 c.c. flask. 

Reagents. — N/10 HCl, methyl-orange (.02 grs. per 100 
c.c). 

Details of Procedure. — Measure into the beaker by means 
of the liter flask 1000 c.c. of the water to be tested. Add not 
more than 10 drops of methyl-orange and titrate in the usual 
way with the N/10 HCl until the acid gives the characteristic 
color of the indicator. Repeat, using 1000 c.c. of distilled 
water. 

Calculation and Statement of Results. — Hardness is 
to be expressed in parts of CaCO, per million. One c.c. N/10 
HCl neutralizes 5 mgr. CaCO,. (Show how this figure is ob- 
tained.) H, therefore, 1000 c.c. of water (1,000.000 mgr.) is 
used for the titration, each c.c. of N/10 HCl must equal 5 parts 
of CaCOg per million. 

Note. — The value here obtained is not taken as a measure 
of the temporary hardness unless the absence of sodium carbon- 
ate or bi-carbonate has been shown by the result of the de- 
termination of permanent hardness (q. v.). 
Determination of the Permanent Hardness of Water. 

Principle of the Method. — If sodium carbonate is added 
to water containing calcium and magnesium salts, the sodium 
carbonate reacts with the alkaline earths precipitating the calcium 
and magnesium carbonates. The NaoCO., thus consumed is 
therefore a measure of these salts. 



Apparatus. — Evaporating dish (11 cms.), 100 c.c. pipette, 
stirring rod, beaker, burette, steam bath, funnel, filter paper. 

Reagents.— N/10 HCl solution, N/10 NaXO.^ solution, 
methyl-orange (.02 grs. per 100 c.c.). 

Details of Procedure. — Measure by means of a pipette 100 
c.c. of the water to be examined into a clean evaporating dish. 
Add a drop or two of methyl-orange and then from a burette 25 
c.c. N/ 10 NaoCOj, or an amount sufficient to make the water 
strongly alkaline. Evaporate to dryness on the steam bath, then 
take up with a small amount of distilled water. The solution 
should show a distinct yellow color. If this is not the case, 
sufficient Na2C03 was not added in the first place, consequently 
more must be added and the evaporation repeated. If the yellow 
color is obtained, filter off the insoluble calcium carbonate, wash 
the precipitate and paper with distilled water until free from 
alkalinity. Titrate the excess of alkali in the filtrate with N/10 
HCl until the characteristic color for methyl-orange in acid 
solution is obtained. The difference between the amount of 
alkali added and the amount found in the titration is the amount 
of NaaCOg used in precipitating the calcium and magnesium 
salts, which produce the permanent hardness. 

Calculation of Result. — The calculation is made in the 
usual manner. Hardness is expressed in parts per million CaCOg. 

Volumetric Determination of Free Carbonic Acid. 

Principle of the Method. — The principle of the method 
depends upon the following reactions : 

a. CO, + NaoCOs -f H.,0 = NaHCOg. 

b. NaXOg + HCl = NaHCO., + NaCl. 

Since phenolphthalein is neutral toward bicarbonate, it may 
here be chosen for indicator. 

Apparatus. — 250 c.c. beaker, stirring rod, 100 c.c. pipette, 
2 burettes. 

Reagents.— N/10 Na.CO^ and N/10 HCl solutions, phe- 
nolphthalein, neutral alcohol. 

Details of Procedure. — By means of the pipette measure 
into the beaker 100 c.c. of the water to be tested. Add two or 
three drops of phenolphthalein, then 10 to 15 c.c. of the neutral 
alcohol. From one of the burettes run into the water a known 



volume of the N/10 NaXOg solution sufficient to give a decided 
red color to the indicator. Now determine the excess of alkali 
added by titration with N/10 HCl. During this titration it is 
necessary to keep the solution rotating rapidly, otherwise local 
excess of acid might carry the reaction to the point of releasing 
carbon dioxide from the bicarbonates. 

Calculation of Results. — By reference to reaction (b) 
under "Principle of the Method/' it is noticed that when titrat- 
ing normal carbonates with acid, phenolphthalein being the in- 
dicator, only half the quantity of acid required for complete 
neutralization is consumed. Consequently, in determining the 
excess of NaaCO.,, the volume of HCl used in the titration must 
be doubled in order that it read in terms of normal carbonate. 
When the number of c.c. Na^COa in excess has been found, 
subtract it from the total number added. The remainder, of 
course, must be NaXOa equivalent to the acidity of the water. 

The Effect of Iron in Water Used for Laundry Purposes. 

Outline of Procedure. — In order to observe the effect of 
iron in water used for laundry purposes, fabrics are washed in 
water containing ferrous bicarbonate and the results noted. 

Apparatus. — Balance and weights, watch glass, large cas- 
serole, piece of clean white cloth,. 2 test-tubes with corks to fit. 

Reagents. — Water containing free carbonic acid and dis- 
solved air, solution containing ferrous bicarbonate approximately 
50 parts per million, soap or soap solution. 

Details of Procedure. — (a) Weigh out 0.13 to 0.16 grams 
of ferrous sulphate, and 0.14 to O.lfi grams of sodium bicarbonate 
(NaHCO^). Dissolve first one then the other in a liter of 
aerated distilled water, through which COo has been bubbled for 
two or three minutes. The following reaction then takes place : 
FeSO, -f NaHCO., = FefHCO,). -f Na,SOt. 

Transfer the bulk of this solution to the casserole. Soap 
the white cloth in exactly the same way as is done in washing 
process, then allow it to stand in the water over night. After 
standing, remove the cloth and examine carefully. (?). 

(b) Take two test tubes, fill one, half full of distilled water 
and the other, half full of the water containing iron. Into each 
introduce a few scraps of soap, then stopper and shake. After 



a few minutes compare the colors of the liquids in the two tubes. 
(?). , 

Question. — Show by reactions how it is possible to obtain 
iron rust stains on fabrics washed in water containing ferrous 
bicarbonate. 

Method for the Determination of Iron in Water. 

Principle of the Method. — Water is freed from organic 
matter. The iron is oxidized to the ferric state, then converted 
to thiocyanate, this being recognized by its characteristic red color. 
In order to make the determination quantitative, the color pro- 
duced by the ferric thiocyanate from the water being examined, 
is compared with colors obtained by similar procedure from 
waters containing known amounts of iron. 

Apparatus. — Evaporating dish (11 cms.), 100 c.c. pipette, 
steam bath, 2-100 c.c. Nessler tubes of equal diameter, 100 c.c. 
graduated cylinder and siphon, liter flask. 

Reagents. — HCl (1-1), KMnO^ solution (5 grams per liter), 
KCNS solution (20 grs. per Hter), standard ferric solution pre- 
pared by dissolving 0.1 gr. of pure iron wire in a little HCl, 
adding a few drops of KMnO^, then diluting to a liter. 

Details of Procedure. — Measure into the evaporating dish 
100 c.c. of the sample of water by means of the 100 c.c. pipette, 
and add 5 c.c. of HCl, then evaporate to dryness on the water 
bath. When the residue is absolutely dry, ignite the contents 
of the dish over a small flame of the Bunsen burner until the 
organic matter is destroyed, indicated by the disappearance of 
all carbonaceous matter. Now add 5 c.c. of HCl (1-1), dilute 
slightly, always keeping in mind that the total volume of the 
solution must never exceed the capacity of the Nessler tube ; 
filter and wash. Add KMnOj, a few drops at a time, until the 
slight pink color thus obtained disappears in not less than 5 
minutes, and then add 10 c.c. of the KCNS solution. Rinse into 
a 100 c.c. Nessler tube, dilute to the mark, and mix thoroughly. 
Next prepare in an exactly similar manner another tube, using 
distilled water and 10 c.c. of the standard ferric chloride solu- 
tion. Compare the colors of these two by looking through the 
depth of the liquids. By means of the glass siphon of narrow 
bore tubing, siphon out a portion of the contents of the tube 



having the deeper tint. Compare the tints again and continue 
the siphoning cautiously until the tints are of equal intensity. 

Calculation of Results.^ — ^When the tints are of equal 
intensity, there are equal quantities of iron in each tube. Meas- 
ure the number of c.c. of the standard solution and calculate the 
weight of iron contained therein, knowing the quantity of iron 
contained in the original 100 c.c. of the standard. This is the 
weight of iron in the quantity of solution in the second tube. 
Measure the number of c.c. contained in the second tube and 
calculate, if necessary, the quantity of iron in 100 c.c. of the 
solution. This is the weight of iron contained in 100 c.c. of 
the water under examination. Express it in parts per million. 

Errors. — It is necessary that the preparation of the color 
from the standard and the unknown water be made at exactly 
the same time and under the same conditions, for the color is 
apt to change with time. The Nessler tubes must be of equal 
diameter. Why? Rust from iron utensils, etc., must not find 
access to the vessels used. 

Coagulation of Clay and Mud. 

Principle of the Method. — If a flocculent precipitate is 
formed in water containing clay or mud in suspension, this 
precipitate will settle on standing, and in doing so will carry 
the suspended material with it, thereby clarifying the water. 

Apparatus. — A tall beaker or cylinder. 

Reagents. — Aluminum sulphate, calcium hydroxide solu- 
tion. 

Details of Procedure.- — Fill the beaker or cylinder two- 
thirds full with turbid water (water having clay or mul in 
suspension), add approximately 0.5 grams of powdered aluminum 
sulphate AL (SO^)^. Allow to stand until the salt has a chance 
to dissolve. Now add, without stirring, 10-15 c.c. of lime water 
Ca(OH)2. Allow the water to stand and note the results. 

Questions. — Write the reactions on which the principle of 
this experiment is based. 

What material removes the suspended matter? 

What becomes of the secondary product of the reaction? 

Some Practical Questions. — 1. From the knowledge ob- 
tained from the foregoing experiments, show by reactions the 



effect of each of the following upon hard waters : Borax, 
washing soda, caustic soda, alum. 

2. Calculate the quantity of any two of the above salts 
necessary to soften the water you analyzed. 

3. Why is iron an objectionable ingredient in water used 
for laundry purposes? 

4. What would you infer if in the determination of perma- 
nent hardness you found in titrating back the excess of alkali 
exceeded the total amount added? How would this figure affect 
the figure obtained for temporary hardness? 

5. State briefly the effect of iron in water used for washing. 
Calculate the parts per million of iron in the water used in the 
experiment, "The Effect of Iron in Water Used for Laundry 
Purposes.'' 



B. SOAP. 

Preparation of Soap (Hard). 

Principle of the Method. — Soap is prepared according to 
the following chemical equation : 

(C,, H35 COO), C3H, -f 3Na(OH) = 
3Ci, H35 COONa 4- C3H5(OH)3. 

Reagents. — Sodium hydroxide, fat or oil, salt. 

Details of Procedure. — Dissolve 15 grams of caustic soda 
in 120 c.c. of water. Place 60 grams of tallow in the casserole 
and pour half the lye solution upon it. Add 50 to 60 c.c. of 
water and boil for three-quarters of an hour. From time to 
time replace the water lost by evaporation. After boiling the 
stated time, add the remaining 60 c.c. of the lye solution and boil 
for an hour more. Water should again be added as in the early 
stages of the boiling, but finally the volume may be allowed to 
diminish one-third. At this stage, add 20 grams of sodium 
chloride, boil again for ten minutes and then allow to cool. The 
soap will rise to the top of the solution. Remove the cake, press 
out the contained liquid, dry between filter papers and then ex- 
amine. 

Note.— Keep this sample of soap for future use. At some 
time determine its quality. 



10 

Hydrolysis of Soap. 

Principle of the Experiment. — Water hydrolyzes soap 
as follows : 

Q,H,, (COONa) + H,0 = Q.H.^, COOH + NaOH. 

Now, since sodium stearate is a highly ionized substance, 
while the free acid is hardly ionized at all, the result of the 
interaction of the water with the sodium salt must be the pro- 
duction of hydroxidion (OH) in the solution. 

Details of Procedure. — To two or three grams of soap add 
50 c.c. of alcohol and heat in a beaker on the steam bath until 
all the soap is in solution. At this point cool, and then add five 
to ten drops of phenolphthalein. Dilute slowly and observe the 
results. ( ? ) . 

A Study of Soap Solutions. 

Object of the Experiment. — To study the tendency of 
aqueous soap solutions, to wet oil or oily substances and to 
emulsify them. 

Reagents. — Neutral or red litmus paper, kerosene, dilute 
lye, soap solution (water), pure water. 

Details of Procedure. — Cut a piece of litmus paper G cms. 
larger than tlie diameter of a beaker. Place the paper over the 
mouth of the beaker, draw it down on the sides until it is 
tight like the head of a drum and then secure it with a rubber 
band. Add enough kerosene to oil the entire surface of the 
paper. Near one e(]ge of the head allow a single drop of lye 
to fall from a stirring rod. In another place repeat with a drop 
of soap solution, while in a third add a single drop of cold 
water. Note the results. (?). Allow to stand for some time 
and again examine. 

Ouestions.^ — 1. In washing, is it the lye formed by hydrolysis 
of the soap or the soap itself, that combines with the oil and 
grease that is present? 

A Study of Soap Solutions (Continued). 

Orject of the Experiment. — First, to show the ease with 
which soap solutions penetrate oils. Second, to show that pure 
water has not the same property. 



11 

Apparatus. — 500 c.c. beaker, glass tubing 4 mm. in cross 
section, large rubber stopper (one hole). 

Reagents. — Soap solution. 

Details of Procedure.— Seal one end of a piece of glass 
tubing, then cut it about four centimeters from the sealed end. 
Place the sealed end in the hole of the rubber stopper, the 
stopper thereby acting as a small stand. Fill the glass tube 
with cottonseed oil, then place the whole in the beaker. Add 
water carefully by pouring the water carefully down the side 
of the beaker until the top of the tube is covered by at least an 
inch of water. Observe the effect if any of the water upon 
the oil in the tube. Now add strong soap solution, 5 c.c. at a 
time, and observe after each addition. (?). 

Question. — What aid is given by this experiment in answer- 
ing the question. What makes soap and water cleanse oily fabrics? 

A Study of Soap Solutions (Continued). 

Object of the Experiment. — To compare the surface 
tensions of soap solutions and water by means of "capillarv 
rise." 

Apparatus. — Two capillary tubes of the same bore, two 
small crystallizing dishes, a centimeter rule, iron stand with two 
clamps. 

Reagents. — Soap solution, pure water. 

Details of Procedure. — Place some soap solution in one 
of the crystallizing dishes. Fill the second with pure water to 
exactly the same height as the first. Place a capillary tube in 
each of the iron clamps attached to the iron stand, then lower 
one into the pure water and the other into the soap solution. 
Note the results. Allow the tubes to stand until there is no 
increase in the height of either column. Now measure the 
capillary rise in each case and compare. 

Question. — What is the relation of the height of the 
column to the surface tension? 

A Study of Soap Solutions (Continued). 

Object of the Experiment. — The object of the experi- 
ment is to measure the relative sizes of drops formed, in soap 



12 

solutions of various strengths, by an oil, as e. g., kerosene. It is 

possible by this method to grade soaps according to their detergent 

powers. 

Apparatus. — One tall beaker (12 cms.), glass tubing 4 mm. 

in cross section, iron stand and clamp, Bunsen burner. 
Reagents. — Kerosene, soap solutions. 

Details of Procedure. — Heat one end of 
the glass tubing in the blue flame of the Bunsen 
burner until the bore is only the thickness of a 
hair, then flatten it out as shown in the sketch, 
at C. Now bend the tubing until it is in the 
shape shown. Cut the limb A-B, 25 to 26 cms. 
in length. Four centimeters from the end "A" 
make a scratch "D" with the triangular file, and 
another "E" 8 cms. below the first. 

Prepare 500 c.c. of an N/10 sodium oleate 
solution and prepare from this by dilution 500 c.c. 
N/20 sodium oleate, from the N/20 prepare by 
dilution N/40, and from the N/40 prepare N/80. 
Place a portion of each of these soap solu- 
tions in suitable beakers to the same height in 
each case. Also provide a beaker containing pure 
water. Fill the dropper with standard kerosene 
and clamp it in a vertical position in one of the 
beakers, the bend resting on the bottom of the 
beaker. Allow the kerosene to flow and count 
the drops as they rise from the orifice "C," while 
the liquid in the main limb passes from "D" to 
"E." Repeat three times and average the re- 
sults. 

Repeat the experiment with each of the soap 

solutions mentioned above and with pure water. 

Plot the results in the form of a curve, using the number 

of drops as ordinates and the concentrations of the solutions as 

abscissae. 

Repeat the above, using several commercial soaps. 
Calculation of the Result. — The ratio (drops given by 
soap under examination. Drops given by standard soap of the 



13 

same strength) is a measure of the detergent power. 

Errors. — Beakers must be filled to the same height in 
every case, and the temperature must be the same. 

Note. — Count the drops formed in skimmed milk, soap 
bark solution and any other foaming liquids. 

Determination of Moisture (Direct Method). 

Apparatus. — Aluminum dish, weights. 

Details of Procedure.— The sample is obtained by cutting 
the sample cake of soap in half, then shaving thin layers from 
the freshly exposed surfaces. Care should be taken to cut en- 
tirely across the surface, for the inside of the cake might have 
a different moisture content than the outer layer. 

Accurately weigh the aluminum dish. Place about two grams 
of the finely shaved sample into the dish and weigh again quickly 
to nearest centigram. The difiference between the two weights 
equals the weight of sample taken for the determination. . Heat 
in the air oven at a temperature 105 degrees for two hours, 
allow to cool in a desiccator and weigh again. Repeat the heat- 
ing for a half hour, cool and weigh as before. These weights 
should be constant. 

Calculation of Result.— Per cent, moisture = 100 (Loss 
of weight due to evaporation) /(Original weight of sample). 

Note. — This method is not absolutely accurate, due to the 
possibility of the loss of some volatile oils during the heating. 

Determination of Moisture. 

Principle of the Method. — By heating soap in an an- 
hydrous solvent of high boiling point, the moisture may be ex- 
pelled while the solid soap is held in solution. 

Apparatus. — Porcelain evaporating dish (8 cms.), balance 
and weights, Bunsen burner, asbestos gauze, thermometer. 

Reagents. — Oleic acid or paraffin. 

Details of Procedure. — Place about 8 to 12 grams of oleic 
acid in the evaporating dish and heat to 120 degrees until all 
the water is expelled. The temperature is determined by sus- 
pending a thermometer in the acid. Regulate the height of 
the Bunsen flame until it is just high enough to maintain the 
acid at the required temperature, 120 degrees. Keep the flame at 
this height until the experiment has been completed. 



14 

Allow the anhydrous acid and dish to cool in a desiccator 
and then weigh accurately. Now add a sample of soap obtained 
as directed above, equal to about one-third the weight of the 
acid, and weigh once more. Place the dish on the tripod over 
the regulated flame and heat until the soap is dissolved and 
the moisture expelled. (Do not have the thermometer in the 
liquid during this heating.) Cool in a desiccator and weigh. 

Calculation of the Result. — Per cent, moisture = 100 
(Loss of weight by evaporation) /(Weight of sample). 

Note. — Paraffin may be substituted for oleic acid. 

The heating, as a general rule, does not take more than 
fifteen minutes. 
Determination of Alkali. 

Apparatus. — Erlenmeyer flask (250 c.c), steam bath, bu- 
rette. 

Reagents. — Neutral alcohol, phenolphthalein, N/10 acid. 

Details of Procedure. — Treat a freshly exposed portion 
of the soap with a drop of phenolphthalein, and if no red color 
is produced, free alkali is not to be expected. 

Accurately weigh a sample of the soap, say two grams, 
transfer it to an Erlenmeyer flask and dissolve in 100 c.c. of 
neutral alcohol. Filter if there is imdissolvecl carbonate or 
other residue, wash with alcohol, add phenolphthalein and titrate 
with standard acid (N/10). 

Calculation of the Result. — Express the free alkali as 
per cent, of sodium hydroxide. 

Note. — If the alcoholic solution reacts acid with the indi- 
cator, reverse the procedure, titrate with standard alkali and 
calculate the resultant free fatty acid as oleic acid. 

If the soap contains both free alkali and acid, this method is 
open to objection, for during the heating of the alcoholic solu- 
tion, some of the free alkali may neutralize a portion of the 
free acid and thereby give unreliable results. 

C. BLUING. 

Prussian Blue. 

Object of the Experiment. — First, to prepare Prussian 
Blue by double decomposition between potassium ferrocyanide 
and ferric salts, as : 



15 

■i: FeCl, + 3 K,FeCN, = Fe, (FeCN,),, + 12 KCl. 

Second, to examine the properties of the substance. 

Details of Procedure. — Weigh out 0.7 grams of potassium 
ferrocyanide and 0.5 grams of ferric chloride. Dissolve sepa- 
rately in 50 c.c. of distilled water. When each has entirely dis- 
solved, add one to the other. ( ?). 

Divide into two portions and filter one of them. 

a. Transfer a portion of the precipitate to a test tube, add 
a few crystals of oxalic acid and warm. (?). Dilute and ex- 
amine. (?). 

b. Place a second portion of the precipitate in an evaporat- 
ing dish and add lye. ( ?). 

c. To a third portion of the precipitate in an evaporating 
dish, add an acid. (?). 

Wash the second main portion several times by decanta- 
tion with hot water and pour the washings through a filter. Test 
a portion of the filtrate for chloride. (?). Note the color of 
the filtrate. (?). When the decanted liquid begins to show a 
decided blue color, pour the precipitate upon the filter and con- 
tinue the washing with hot water. Save the filtrate. Test the 
filtrate for chloride. (?). 

Questions. — 1. Of what practical value is the knowledge 
obtained in this experiment? 

2. What name is given to solutions similar to that obtained 
by washing the second precipitate? 

Properties of Ultramarine. 

Object of the Experiment. — To examine the properties of 
ultramarine. 

Details of Procedure.- — Crush a "bluing ball" into small 
pieces. Place some of them in a test tube, add sufficient water 
to cover them, then enough acid to make the solution acid. Hold 
a filter paper wet with lead acetate or nitrate over the mouth 
of the tube. Heat if necessary. (?). Repeat, using sulphuric 
acid. (?). To a second portion of the crushed material, add 
sodium or potassium hydroxide. Test with the lead paper. (?). 

Questions. — 1. What is the stability of ultramarine toward 
acids and alkalies? 

2. What is its solubility in water? 

How would you rank it as a bluing? Give reasons. 



16 

3. \\'hat was the original source of ultramarine. 

4. How is it prepared artificially? 

5. In what form is it usually found when intended for 
laundry use ? 

(). What have you learned as to the stability of ultramarine? 

D. BLEACHES. 

Bleaching Action of Chlorine and Hypochlorites. 

Object of the Experiment. — To prepare hypochlorous 
acid, sodium hypochlorite, javelle water and bleaching powder, 
and to examine each for its bleaching properties. 

Apparatus. — Small beaker, chlorine generating flask. 

Reagents. — Solution of sodium hydroxide (10 per cent.), 
hydrochloric acid, potassium permanganate or manganese di- 
oxide, litmus paper. 

Details of Procedure. — Pass chlorine gas into 100 c.c. of 
the 10 per cent. Na(OH) solution until it no longer gives a 
test for alkali with litmus. Examine this solution for bleaching 
properties by dipping into it colored fabrics. Add an excess of 
hydrochloric acid. Is there any evidence of decomposition? 
Note the odor. The solution is commonly known as javelle 
water. It contains sodium hydrochlorite (NaClO) and sodium 
chloride (NaCl). Write the reactions for its formation. 

To about 50 c.c. of the javelle water, add 50 c.c. of 2N HCl 
and distil. Examine the distillate for bleaching properties. 
What does it contain? 

Slake 25 grams of quick lime, avoiding excess of water. 
Saturate it with chlorine. What is it? To about 20 grams 
of the material suspended in water, add sodium carbonate until 
no further precipitation takes place. Filter the solution and 
compare it with the sodium hypochlorite prepared above. Write 
the equation. 

Note. — The bleaching action of hypochlorous acid and hypo- 
chlorites depends upon the readiness with which they part with 
oxygen. Compare the decomposition of chlorine water in direct 
sunlight. ( ?). 

A solution of chlorine in water may be quickly and con- 
veniently prepared by the addition of hydrochloric acid to an 
aqueous solution of a per salt (e. g. KMnO^). 



17 

Hydrogen Peroxide as a Bleaching Agent. 

Object of the Experiment. — To examine the bleaching 
properties of hydrogen peroxide on feathers, hair and ivory. 

Details of Procedure. — Fill a test tube two-thirds full 
of hydrogen peroxide. Add ammonium hydroxide, drop by drop, 
examining after each ackUtion, until small bubbles appear on 
the side of the tube. Insert the material to be bleached into 
the solution and examine from time to time. 

Questions. — 1. Upon what does the bleaching action of the 
peroxide depend? 

2. Did you notice any tendency of the bleached material to 
rot? If so, to what do you attribute the rotting? 

REMOVAL OF STAINS FROM FABRICS. 

Methods of Procedure. 

Ink Stains. — Ordinary writing fluid consists of a solution 
of tannate of iron and an anilin dye, drawing inks contain finely 
divided carbon in suspension, indelible inks frequently contain 
silver nitrate, red inks are usually a solution of anilin dye. 

Fruit Stains. — Due either to coloring matter naturally 
present or to colored products formed by oxidation. 

Grease Spots.— Dirt, of course, accumulates on grease, 
causing a discoloration which cannot be removed till the grease 
is dissolved. 

I. Physical Methods of Removal. 

Chiefly of value with fresh stains. 

Treat the article with a chemically inert, emulsifying de- 
tergent, as e. g., skimmed milk, soap bark, stale beer, gum solu- 
tions. 

Take a piece of white linen or cotton having an ink stain 
on it and allow to soak for some time in skimmed milk. Try 
also some of the other substances mentioned above. 

2a. Chemical Methods of Removal (Solvents). 

This treatment requires a knowledge of the cause of the 
stain, as e. g., iron rust or iron ink. 



18 

Take a piece of white linen or cotton on which are rust stains. 
Immerse in a tepid soh;tion of hych-ochloric acid 2N, watching 
carefully till the stain is seen to be dissolved, then wash thor- 
oughly till free from acid. 

Take a piece of cloth which is stained with a grease spot. 
Treat the dry cloth with a fat solvent, such as carbon tetra- 
chloride, chloroform, ether or gasoline. Carbon tetrachloride and 
chloroform have the advantage of not being inflammable. 

2b, Chemical Methods of Removal (Bleaching). 

This is useful in removing organic stains, as indelible pencil. 
Sulphur dioxide, hydrogen peroxide or chlorine compounds may 
be used. 

Take a piece of white cloth on which are spots of red ink. 
Remove them with bleach. Try sulphur dioxide, ammonical 
peroxide of hydrogen and chlorine or javelle water. 

PATENT DUST CLOTH. 

Details of Procedure. — Place portions of a patent dust 
cloth in a Soxhlet extractor and extract with ether. Cautiously 
evaporate the ether and weigh the residual oil or grease. Cal- 
culate the grams of oil per square foot of dust cloth. 

Endeavor to identify the oil by determining the specific gravity 
saponification equivalent, iodine number, viscosity, non-saponifi- 
able matter. ( Get special instructions for each of these deter- 
minations.) 

CLEANSING AND POLISHING METALS. 

Method of Procedure.— Metals are usually tarnished by a 
layer of oxide or sulphide. This is best dissolved by appropriate 
solvents, such as do not attack the metals to any appreciable 
extent. The polishing is accomplished by friction or pressure 
of a substance which is softer than the metal, and therefore does 
not abrade it, but polishes by causing an actual flow of the 
metal under the applied pressure, with the result that all the 
abrasions are filled in and a perfectly smooth surface results. 



19 

Ammonium hydroxide dissolves many metallic oxides, espe- 
cially that of copper. Potassium cyanide is an excellent solvent 
for silver compounds, but is objectionable because of its poisonous 
character. 

As polishing powders, there may be mentioned rouge (or 
finely divided iron oxide), whiting (finely divided chalk) and 
less common in any but technical work, alumina. The polishing 
is done with the wet powder. 



II. AIR AND ITS EXAMINATION. 

A. DUST. 

Principle of the Method.— A quantity of dust is col- 
lected by exposing a glass plate to the air. It is then examined 
under the microscope. 

Apparatus. — Glass microscope slides, microscope and acces- 
sories. 

Reagents. — Solution of Canada balsam in alcohol. 

Details of Procedure. — Carefully cleanse the slides. Paint 
them with the solution of Canada balsam and expose to the air for 
a definite time. Place the cover glass on the slide and examine 
under the microscope, endeavoring to identify the objects seen. 

B. HUMIDITY. 

Principle of the Method. — If a thermometer, whose bulb 
is kept wet with a film of water, be exposed to dry air or air 
containing less than enough moisture to saturate it, water evapor- 
ates from the thermometer, absorbing heat from the mercury 
and the glass, so that a lower temperature is recorded. The 
lowering of the temperature is a measure of the humidity of 
the air, the difference between the "dry" and "wet" bulb ther- 
mometer being a maximum in perfectly dry air and zero in 
saturated air. 

Details of Procedure. — Read the several "wet" bulb ther- 
mometers with their associated "dry" bulbed ones, at regular 
(say half-hour) intervals, noting the conditions in the room with 
respect to ventilation, i. e., whether windows are up, number of 
people in the room, number of burners burning, etc. 

Calculation of Results. — An empirical table gives, for 
each dry bulb temperature and difference between "wet and dry," 
the vapor pressure of the moisture in the air. Divide this by 
the vapor pressure for zero difference of "wet 'and dry," and 
we have the relative humidity. Calculate the relative humidity 
of the outdoor air when heated to the temperature of the room 
without the loss or addition of moisture. 



21 

Note. — The excess humidity of indoor air over that out of 
doors (when calculated to the indoor temperature), is a good 
measure of the pollution of the atmosphere by exhalations or 
combustion products. 

C. CARBON DIOXIDE IN THE AIR (METHOD OF 
PETTENKOFER). 

Principle of the Method. — A measured volume of air is 
exposed to a known volume of standard barium hydroxide solu- 
tion, the carbon dioxide of the air being absorbed and precipi- 
tated as barium carbonate. The excess of barium hydroxide is 
determined by titration with standard acid. 

Apparatus. — Large glass globe holding several liters, bel- 
lows, 2 burettes, pipettes (50 and 100 c.c). 

Reagents. — Dilute hydrochloric or oxalic acid such that 1 c.c. 
is equivalent to 0.5 c.c. carbon dioxide gas at zero and ?()() mm. 
pressure, phenolphthalein solution, 400 c.c. beaker and stirring 
rod. 

Details of Procedure. — By means of the bellow^s fill the 
large glass globe with air to be tested. Avoid contamination 
from the breath while taking the sample. Add 100 c.c. of the 
barium hydroxide solution by means of the pipette (do not 
blow out the pipette). Stopper the globe and allow to stand 
for some hours, shaking the contents about occasionally, so as 
to wet the walls. 

In the meantime standardize the reagents. Prepare the 
acid by dilution of a stronger solution whose concentration is 
accurately known. Titrate measured portions of this acid with 
the barium hydroxide. 

After several hours, draw out 50 c.c. of the solution from 
the globe and titrate the excess barium hydroxide with the 
acid. 

Calculation of Results. — 

50 c.c. barium hydroxide require "a" c.c. acid 

100 c.c. barium hydroxide require 2a c.c. of acid 

50 c.c. barium hydroxide require (after exposure) "b" c.c. acid 

100 c.c. barium hydroxide require (after exposure) 2b c.c. acid 

Therefore, c.c. CO^ in the volume of air taken = (2a-b) 0.5 
c.c. at zero and 700. 

Per cent. CO, = 100 (a-b) /(volume of air— 100 c.c). 



III. HEAT. 



A. TO MAKE WATER-GAS. 

Principle of the Method. — When steam is lead over car- 
bon or anthracite heated to a temperature approaching redness, 
the following reaction takes place : 

C + H.O = CO + H^. 

The mixture of equal volumes of hydrogen and carbon mon- 
oxide so obtained is known as water gas. 

Apparatus. — Tube of hard glass or quartz about (i ins. long. 
Bunsen burner, flask and tubes to serve as boiler, bell-jar of 
perhaps a liter capacity. 

Details of Procedure. — Assemble the apparatus (see In- 
structor) and drive steam through the apparatus until the air 
is entirely flushed out. Place the glass bell-jar in position and 
heat the tube containing the coke or coal, until gas begins to 
collect in the bell-jar. Continue heating and passing the steam 
till the jar has become full of gas. 

Note. — 1. Observe the character of the flame of burning 
water gas. 

2. Add 4 c.c. of gasoline to every liter of the water gas. 
Observe the character of the flame of the burning gas thus 
enriched. 

B. BUNSEN FLAME. 

Examine the construction of a Bunsen burner, noting the 
area of the gas orifice at the base of the burner. Arrange an 
apparatus to observe the volume of gas issuing per minute under 
the city pressure, and calculate the linear velocity with which 
the gas passes through the orifice. 

What causes "striking back?" How may it be remedied? 

When is a "Bunsen flame" hottest, when burning yellow, 
when blue but quiet, or when roaring? 

Test the temperatures of the various parts of the flame with 
a platinum wire. 



23 

C. COMBUSTION A MUTUAL PROCESS. 

Take an ordinary lamp chimney and fit it with a doubly 
bored cork at the base. Through the holes in the cork, pass 
two glass tubes, one straight of wide bore (3/16 to 1/4'') the 
second bent at right angles of somewhat smaller bore tubing. 

Connect the bent tube with the gas supply pipe and light 
the gas as it issues from the glass tube. Turn quite low and 
introduce cork carrying tubes into lamp chimney. Turn up the 
gas flame so that it gradually displaces the air from the chimney, 
and note, that on bringing the ends of the tubes together while 
continuing to turn on more gas, that the flame passes from the 
"gas" tube to the "air" tube, and we have a very faint, non- 
luminous flame of air burning in gas. 

D. TO COMPARE THE RATE OF COOLING OF A 

WHITE OBJECT AND A BLACK OBJECT 
UNDER IDENTICAL CONDITIONS. 

Principle of Method. — Two test tubes as nearly alike as 
possible are fitted, one with a white muslin covering, the other 
with black, and filled each with equal quantities of boiling water 
or hot water, at the same temperature. A thermometer is placed 
in each and the temperature is read at minute intervals. We 
then plot a temperature-time curve for each and compare the 
two. (The experiment may, of course, be extended by the use 
of coverings of different materials, as linen, silk, wool, etc., and 
also fabrics of different colors.) 

Apparatus. — Six-inch test tubes, coverings for the same, 
supports for the tubes, thermometer for each tube, perforated rub- 
ber stopper for each tube, watch with second hand, wash bottle 
containing boiling water, large beaker, Bunsen burner and tripod 
with gauze. 

Details of Procedure. — Boil sufficient water in the beaker 
to submerge the tubes. Place the tubes in the beaker and note 
that the water filling each is at the same temperature. Withdraw 
the tubes simultaneously, dry quickly, insert in the coverings, 
place them in the support and commence to read temperatures, 
reading the tubes alternately (or in rotation if more than two), 
so that the temperature of each tube is read at minute intervals. 



24 

Continue until the temperature of the tubes has fallen to within 
five degrees of the room temperature. 

Calculation of Results. — Plot the results to a convenient 
scale on cross-section paper, with temperatures as ordinates and 
time as the abscissae and note which cools the more rapidly. 

Note. — It would be well to silver a tube and carry out the 
experiment in comparison with a plain tube. 

E. PROXIMATE ANALYSIS OF COAL. 

Object of the Experiment.— By making tests to deter- 
mine the quantity of moisture, volatile matter, coke, ash, sul- 
phur and heat of combustion, an analyst may reach a definite 
conclusion as to the quality of the coal. The following methods 
are not for the determination of any definite chemical compounds, 
but their results give a basis for the comparison of coals. 

Details of F^rocedure. — (a) Dctcrviination of Moisture. 
Weigh exactly one gram of coal in a porcelain crucible, which 
has previously been heated, cooled in a desiccator and weighed. 
Place the crucible with its contents in an air oven heated at 
104 to 107 degrees C for one hour. Cool in a desiccator and 
weigh. The loss of weight is equal to the moisture in the 
sample. Express the results as per cent, moisture. (Keep for 
use in the determination of ash.) 

(b) J^olatilc Combnsiiblc Matter. Weigh a large crucible 
and lid, which has previously been heated and cooled in a desic- 
cator. Weigh into it exactly one gram of coal, cover and heat 
with the full flame of the Bunsen burner" for exactly seven min- 
utes. Cool in a desiccator and weigh. In this determination, 
the following conditions are essential. The bottom of the cruci- 
ble must be 6 to 8 cms. above the bottom of the Bunsen burner, 
which must have a clear blue flame fully 20 cms. high when 
burning free. The crucible must be protected from draughts 
during the heating. The upper surface of the lid must burn 
clear. The loss in weight less the moisture in the powdered 
coal is the volatile matter in the coal. Express the result as 
per cent, of volatile combustible matter. 

(c) Coke. The residue in the crucible is coke. 

(d) Ash. Place the crucible containing the coal from which 
the moisture has been expelled, upon its side on a pipe-stem 



25 

triangle. Heat at first with a very small flame, gradually in- 
creasing the heat as the combustion proceeds. Be sure to allow 
free access of air to the crucible. Continue until all black particles 
are burned. The per cent, of coke minus the per cent, of ash, 
gives the per cent, of fixed carbon. 

(e) Heat of Combustion by Calorimeter. The details for 
this determination will be found in the printed pamphlet that 
accompanies the calorimeter. 

Keep the contents of the bomb for the determination of 
sulphur. 

Determination of Sulphur. — Transfer the contents of 
the bomb after the determination of the heat of combustion to a 
400 c.c. beaker. Add 200 c.c. of distilled water. Wash the bomb 
carefully with distilled water and add the washings to the main 
solution. Acidify the solution with HCl and filter. Place the 
beaker upon a tripod, cover with a watch glass and heat to boiling. 

Precipitate the sulphate by adding 10 c.c. barium chloride 
(BaClo) to the boiling solution. If a precipitate does not fall 
immediately, allow the solution to stand over night. 

Filter on a weighed Gooch crucible. Dry, ignite and weigh 
the barium sulphate. Calculate per cent, sulphur in the coal. 

F. DRY DISTILLATION OF BITUMINOUS COAL. 

Object of the Experiment. — Bituminous coal is heated 
without access of air and the products thus formed are examined. 
Apparatus. — Retort. 

Details of Procedure. — Fill a retort one-half full of soft 
coal. Connect the exit of the retort with a train consisting of 
an empty bottle, to collect any liquids that might distil over, a 
second bottle containing wash water and a gasometer constructed 
by the use of small beakers filled with water inverted in a pneu- 
matic trough. ' . 

Heat the coal. Discard the first 200 to 250 c.c. of gas col- 
lected in the gasometer, for it will be air displaced from the ap- 
paratus. Continue the heating until no more gas is evolved. 

Identify the products in the first bottle. (?). 

Add a drop or two of litmus to the water in the second 
bottle. (?). Test for volatile alkali. (?). What is it? 



26 

Set fire to the gas in one of the beakers. What is the char- 
acter of the flame? 

Add lime water to the gas in another beaker. (?). 

Drop a paper wet with lead acetate into a third sample of 
the gas, cover the beaker and examine the paper after a time. 

To a fourth sample, add a weak solution of bromine water 
and shake. 

To still anotlier sample, add a small piece of phosphorous. 

Question. — What do you conclude as to the composition of 
illuminating gas? 

G. PREPARATION OF PARAFFIN WAX. 

Chill about 50 c.c. of paraffin oil in a salt and ice mixture. 
Note the separation of paraffin. Drain off the oil. Melt and 
freeze again. Repeat till the wax is quite free from oil, wash- 
ing with a little benzine if necessary, to facilitate the removal 
of the oil. 

Finally, heat with bone black, filter and chill. We should 
have a piece of white paraffin wax. 



IV. FOOD MATERIALS. 

A. BAKING POWDER. 

I. Identification of the Acid Constituents. 

Object of the Experiment.— To analyze qualitatively for 
the various acid constituents of baking powder and thereby de- 
termine the class to which the powder belongs. 

Apparatus. — Beaker, stirring rod, test tubes, evaporating 
dish, filter. 

Reagents. — Ammonium molybdate, cupric hydroxide, potas- 
sium permanganate, oxalic acid, barium chloride. 

Details of Procedure. — (a) The pozvder contains an in- 
soluble carbohydrate (starch) as filler. Place about 5 grams 
of the powder in a beaker and cover with cold water. After 
the first violence of the action has subsided, stir so as to facili- 
tate solution of all the soluble constituents. Allow to subside, 
then pour through a filter. 
The Residue will contain : 

1. Starch. 

2. Secondary calcium phosphate. 

3. Aluminum hydroxide. 

Examine it as follows: Treat with cold dilute nitric acid 
and filter from the insoluble starch. Place a small portion of 
the nitric acid solution in a test tube, add an excess of am- 
monium molybdate ; warm, shake, and look for the appearance of 
a canary yellow pulverulent precipitate of ammonium phospo- 
molybdate, which indicates the presence of phosphates. 

If phosphates are absent, to the remainder of the nitric acid 
solution add ammonium hydroxide ; the formation of a white 
precipitate of aluminum hydroxide indicates alum in the powder. 
(If this test is found to be positive, apply the test for the detec- 



28 

tion of aluminum compounds, found at the end of the experi- 
ment.) 

If phosphates are present, treat the remainder of the nitric 
acid solution with an excess (2 grams) of pure tin and 5 c.c. 
nitric acid. Evaporate to dryness, take up with nitric acid and 
water, allow to subside in a cylinder, filter from the insoluble 
meta-stannic acid and stannic phosphate, and test the filtrate 
for the presence of alumina by means of ammonium hydroxide 
as above. 

Boil a portion of the Re.sidue with water, cool and add a 
solution of iodine. A blue color indicates starch. 

The Filtrate will contain : 

1. Sodium potassium tartrate. 

2. Secondary sodium phosphate. 

3. Sodium sulphate. 

Examine it as follows : Precipitate in a test tube a small 
quantity of cupric hydroxide by the addition of a solution of 
sodium hydroxide to one of cupric sulphate. Add to this a 
portion of the solution to be tested for tartrates and warm 
gently. Observe whether the cupric hydroxide dissolves with 
the production of a deep blue solution, which does not precipi- 
tate on boiling. 

Place another portion of the solution in an evaporating 
dish and evaporate to dryness. Heat the residue. If it blackens 
with intumescence, emitting odor of burned sugar, we may as- 
sume the presence of tartrates. 

Take another small portion of the Filtrate and add a strong 
solution of potassium permanganate and boil, adding more per- 
manganate if the solution bleaches out. Finally dissolve any 
brown precipitate by the addition of a few crystals of oxalic 
acid. Now test for the presence Of phosphates by means of 
ammonium molybdate as above. 

Take another portion of the Filtrate, acidify with hydro- 
chloric acid and add barium chloride. A white precipitate of 
barium sulphate indicates the presence of sulphates. 

(b) The pozvdcr contains a soluble carbohydrate (lactose) 
as filler. Place about 5 grams of the powder in a beaker and 



cover with water, stir to facilitate the solution and filter from 
the insoluble matters. 
The Residue will contain : 

1. Secondary calcium phosphate. 

2. Aluminum hydroxide. 
Examine it as above. 

The Filtrate will contain : 

1. Lactose. 

2. Sodium potassium tartrate. 

3. Sodium sulphate. 

4. Secondary sodium phosphate. 

Examine it as follows : Evaporate to dryness and heat till 
thoroughly charred. Extract with water. Test the filtrate for 
carbonates, by looking for efifervescence upon the addition of 
acid. Their presence indicates tartrates in the powder. Test 
also for phosphates and sulphates as described above. 

Boil a small portion with Fehling's solution. A red pre- 
cipitate indicates lactose. 

Detection of Aluminum Compounds in Baking Powders 
(Applicable in the Presence of Phosphates). 

Ash about two grams of the material in a thin porcelain 
dish. Extract the residue with boiling water and filter. The 
filtrate will contain the alumina if present in the form of sodium 
aluminate. Add to the filtrate sufficient ammonium chloride to 
give it a distinct odor of ammonia. Alumina is indicated by 
the formation of a white precipitate of aluminum hydroxide. 
Na..Al.A + NH.Cl + H.O = 2Al(OH)3 + 2NH,(OH) 

+2NaCl. 

2. Detection of Ammonium Salts. 

Place about two grams of baking powder in a large test tube, 
add an excess of a solution of sodium hydroxide and warm. 
Notice the odor and hold a piece of wet neutral litmus paper in 
the fumes and observe whether it turns blue. 

3. Determination of Total Carbon Dioxide. 

Principle of the Method. — The baking powder is treated 
with acid, which liberates the carbon dioxide gas. The volume 



30 



of the gas is measured by the displacement of water. Its weight 
is calculated from this volume, knowing the temperature and 
pressure. 

Apparatus. — Special apparatus according to the following 
sketch : 




Weights, 50 c.c. pipette, flat pan scales. 

Details of Procedure. — Assemble the apparatus as shown 
in the sketch. Weigh the beaker "C" to the nearest decigram. 
Weigh from 10 to 15 grams of the baking powder to the near- 
est centigram. Clean and dry the Erlenmeyer flask "A," and 
introduce the weighed powder into it, without loss. Place the 
flask in position and open the stopcock "J" and then pinch clamp 



31 

"F" to equalize the pressure. It is necessary that the outlet 
tube at the end of the apparatus be completely filled with water. 
Close "F" and then "J." Drop exactly 50 c.c. of dilute sulphuric 
acid into the dropping funnel "B." It is absolutely necessary, 
of course, that all joints be air-tight. Place the weighed beaker 
"G" in position. Read the thermometer "T" and the barometer. 
Drop the acid in the tap-funnel into the flask by careful control 
of the stopcock "J." It is necessary that every drop of acid enter 
the flask, but no air, therefore, close the stopcock the instant 
the last portion of the acid enters the bore of the stopcock. 
When all the apparent action in the flask has ceased, boil gently 
for five minutes. Allow the apparatus to return to room tem- 
perature. This may be hastened by surrounding the flask "A" 
with cold water contained in the glass jar "K," until the ther- 
mometer "T" records the original temperature, then replacing 
"K" by a similar jar containing water at room temperature. 

Now bring the liquids in the globe '"E" and beaker "G" to 
the same level. After a few moments close "F," while the levels 
are the same. Remove the beaker "G" and weigh to the nearest 
decigram. 

Calculation of the Result. — Let "W" grams of water 
be the amount displaced at the temperature "T" and the pressure 
*'P," then we have (W-50) c.c. of carbon dioxide at "T" de- 
grees cent., and "P" millimeters mercury pressure saturated with 
moisture. "A" is the aqueous tension at a temperature "T." 
Per cent, carbon dioxide = (W-50) X 273 X (P-a) X .00198 

X 100/(273 -^ t) (weight of baking powder). 
Carbon Dioxide Az'ailabic in the Cold. 

Principle of the Method. — A weighed quantity of baking 
powder is acted upon by water for a definite time at room tem- 
perature, the COo being allowed to escape into the air. The 
residual CO, is then determined as under total carbon dioxide. 

Apparatus. — As in determination of total carbon dioxide. 

Details of Procedure. — ^Weigh 20 to 30 grams of baking 
powder to the nearest decigram. Transfer it to the flask "A" 
without loss, and add 10 c.c. of water for each gram of powder. 
Allow to stand for twenty minutes. Connect up the apparatus 
and proceed exactly as before with the determination of CO^. 



32 

Calculation of Result. — Calculate exactly as in the case 
of total CO,. 

4. Carbon Dioxide Available at 100 Degrees Centigrade. 

Principle of the Method. — A weighed quantity of the 
powder is treated with a definite amount of cold water, then 
heated to boiling and the carbon dioxide allowed to escape in 
the air. The residual carbon dioxide is then determined as 
described before. 

Apparatus. — The same as before. 

Details of Procedure. — Weigh 20 to 30 grams of the 
powder as before and treat with water in the proportion of 10 
c.c. per gram of powder. After effervescence has ceased, heat 
to boiling for five minutes. Cool to room temperature, connect 
with the apparatus and proceed as before with the determination 
of the carbon dioxide. 

Calculation of the Result.^ — The same as before. 

5, Determination of Starch. 

Principle of the Method. — The baking powder is treated 
with cold dilute acid, whereupon all the components of pure 
baking powder, with the exception of starch, are dissolved. The 
insoluble starch is then separated from the soluble salts and 
determined. 

Apparatus. — Measuring cylinder, prepared Gooch crucible 
and filtering apparatus. 

Reagents. — Hydrochloric acid (3 per cent, solution), al- 
cohol, ether. 

Details of Procedure. — Weigh about one gram of the 
powder to the nearest milligram. Transfer to a clean 200 c.c. 
beaker and treat with 150 c.c. of the cold three per cent, acid, 
stirring for fifteen minutes. Filter through a Gooch crucible. 
Wash with water until neutral, and then follow with 15 c.c. of 
alcohol and finally with 15 c.c. of ether. 

Dry the crucible and its contents in the air oven at 110 
degrees for two hours. Cool in a desiccator and weigh. Place 
the crucible over a small flame of the burner for five minutes. 
Gradually increase the heat until it is sufficient to burn ofif the 



33 

starch. When this step is accomplished, cool in the desiccator 
and weigh. 

Calculation of the Result. — Per cent, starch ^ 100 X 
loss of weight on ignition/weight of sample. 

6. Determination of Lactose Used as Filler. 

Principle of the Method. — The lactose is dissolved from 
the powder by treating with water and then determined in the 
solution by the use of Fehling's solution. 

Apparatus. — 250 c.c. graduated flask, 50 c.c. pipette. 

Reagent. — Fehling's solution. 

Details of Procedure. — Weigh 5 grams of the powder. 
Transfer the weighed sample to a small beaker and treat with 
150 c.c. of distilled water for five minutes. Filter if necessary, 
allowing the filtrate to run into a 500 c.c. graduated flask. Wash 
with distilled water until the volume of the water reaches the 
graduation mark on the flask. Mix thoroughly, draw off 100 
c.c. (pipette) and determine the lactose therein as directed under 
milk. 

Calculation of the Result. — Same as under milk. 

B. MILK. 

I. Sampling. 

Before taking a sample for analysis, mix the milk thoroughly 
by pouring it back and forth from one container to another. 

2a. Determination of the Specific Gravity (Pyknometer). 

The weight of a definite volume of milk at 15 degrees is 
divided by the weight of an equal volume of water at the same 
temperature. 

Apparatus. — Pyknometer, balance and weights, thermom- 
eter, two dry beakers. 

Details of Procedure. — Weigh the carefully cleaned and 
dried pyknometer to the nearest centigram. Fill with milk, the 
temperature of which has been adjusted to 15 degrees, being care- 
ful to expel all air bubbles. Weigh again to the nearest centigram. 
Wash the pyknometer thoroughly and fill it with distilled water 
at 15 degrees. Weigh again to the nearest centigram. 



34 

Calculation of Results. — Specific gravity = (weight of 
milk) /(weight of water). 

Note.— Normal milk should range between 1027 and 1033 
specific gravity at 15 degrees. 

2b, Determination of Specific Gravity (Lactometer). 

Principle of the AlETiion. — A floating body sinks in a 
fluid until the weight of the fluid displaced equals the weight of 
the body. From this it follows that the comparative depths of 
flotation of a definite body in various fluids measure the specific 
gravities of the fluids. 

Apparatus. — Lactometer, cylinder, thermometer. 

Details of Procedure. — Place the lactometer in the cyl- 
inder and pour in milk until it floats. Read the specific gravity 
on the stem. Take the temperature of the milk and correct 
the specific gravity by means of the table furnished with the 
instrument. 

Note. — Normal milk should range between 1027 and 1033 
specific gravity at 15 degrees. 

3, Determination of Total Solids. 

Principle of the Method. — If milk is heated to 100 de- 
grees, the vapor pressure is sufficient to evaporate the water from 
it rapidly, though the temperature is not sufficient to decompose 
the organic matter. 

Apparatus. — Flat aluminum dish, balance and weights, 10 
c.c. pipette, steam bath, weighing bottle. 

Details of Procedure. — Accurately weigh the aluminum 
dish to the nearest milligram. Place about 10 c.c. of milk in a 
weighing bottle and weigh to the nearest centigram. Pour the 
milk without loss into the aluminum dish. Weigh the bottle 
again to the nearest centigram. 

Heat the dish on the steam bath for two hours. Dry it and 
cool in a desiccator. Weigh the dish with its contents to the 
nearest milligram. 

Calcul.\tion of Results. — Per cent, total solids = 100 
(weight of solid residue) /(weight of milk). 

4. Determination of Ash, 

Principle of the Method. — The milk is treated with nitric 
acid to assist in the oxidation of the organic matter, then evapo- 



35 

rated to dryness and finally ignited to burn ofif the carbonaceous 
material. The residue is the mineral matter or ash. 

Apparatus. — Thin porcelain dish, Bunsen burner, tripod, 
triangle, desiccator, balance and weights. 

Details of Procedure. — Carefully weigh the porcelain dish 
to the nearest milligram. Transfer to it from a weighing bottle 
a quantity of milk weighed accurately to centigrams (approxi- 
mately 20 grams). Add 6 c.c. of nitric acid and evaporate on 
the steam bath. When dry, place on the tripod and heat cau- 
tiously to dull redness until the residue is perfectly white. Cool 
in a desiccator and weigh to the nearest milligram. 

Calculation of Result. — Per cent, ash = 100 (weight of 
ash) /(weight of milk). 

5a. Determination of Fat (Babcock Method). 

Principle of the Method. — When concentrated sulphuric 
acid is added to milk the emulsion is destroyed, the milk is 
curdled, the casein subsequently dissolved. The fat globules 
coalesce in a melted state at the top of the liquid. By whirling 
in the centrifuge, the separation of the fat is hastened and ren- 
dered complete. 

Apparatus. — Babcock centrifuge, Babcock test bottles, 17.6 
c.c. pipette, 17.5 c.c. graduate, wash bottle containing boiling 
water. 

Reagents. — Commercial sulphuric acid specific gravity 1.83 
to 1.84, a liter of boiling water. 

Details of Procedure. — Measure by means of the pipette 
17.6 c.c. of the milk into a test bottle. Add one measure (17.5 
c.c.) of the sulphuric acid. Mix thoroughly until the casein is 
thoroughly dissolved. Place the bottle in a pocket of the centri- 
fuge. Balance the machine by placing another bottle similarly 
prepared in the opposite pocket. Fill the pockets with boiling 
water and whirl for five minutes. Add distilled water to the 
bottles until they are filled to the top of the graduation and 
whirl again for one minute. All the fat should now be found 
as a clear yellow continuous layer in the graduated neck of the 
bottle. If this is the case, read the upper and lower limits of the 
fat layer. 

Calculation of Results. — The difiference of the two read- 
ings is the per cent. fat. 



36 

Note. — The average per cent, of fat in milk is 3.5 to -i.O 
per cent. 

5b. Determination of Fat (Gravimetric Method). 

Principle of the Method. — Fat is the only component of 
the dried milk residue soluble in anhydrous ether. 

Apparatus. — Soxhlet extraction apparatus, paper thimble, 
balance and weights, tripod, wire gauze. Bunsen burner, large 
iron stand clamp, steam bath, oven, strip of fat free filter paper, 
2^ by 22 ins., liter beaker. 

Reagents. — Anhydrous ether. 

Details of Procedure. — Roll the strip of filter paper into 
the form of a cylinder of a smaller diameter than the weighing 
bottle. Wrap around it a piece of fine copper wire allowing four 
or five inches of the free end of the wire to serve as a handle. 
Place about 5 grams of milk in the weighing bottle. Weigh 
accurately to the nearest centigram. Dip the paper coil into the 
bottle and allow all or as much of the milk as possible to be 
absorbed. Remove the coil and hook the copper wire over a glass 
rod, which is placed across the top of an empty beaker. Weigh 
the bottle again to the nearest centigram, place the beaker con- 
taining the coil on the steam bath and heat until the paper is 
dry, finishing in the oven, the temperature of which never exceeds 
100 degrees C. 

Weigh the receiving flask of the Soxhlet apparatus. Trans- 
fer the dried paper coil to the thimble of the extractor. As- 
semble the parts of the apparatus and add sufficient anhydrous 
ether down the top of the condenser to cause the syphon to act, 
then 30 to 40 c.c. in excess. Heat cautiously, regulating the 
flame to the proper height, so that the ether boils quietly. Ex- 
tract for at least two hours. Evaporate the ether extract and 
washings in the flask by placing it on the steam bath and finally 
drying in an air oven at 100 degrees cent., while aspirating air 
through the flask. Cool and weigh. 

Calculation of Results. — Per cent, of fat = 100 (weight 
of fat) /.(weight of milk). 

Sources of Error. — Avoid placing more milk in the weigh- 
ing bottle than the paper can absorb, otherwise an error due to 
selective absorption may occur. Do not allow the milk soaked 



37 

coil to come in contact with any object lest a portion of the 
milk be lost. 

If the coil is not thoroughly dry before extraction or the 
ether used is not anhydrous, water soluble substances (sugar) 
may be dissolved in addition to the fat. 

6. Determination of Milk Sugar. 

Principle of the Method. — The proteins of the milk are 
precipitated by adding copper sulphate solution, the fat being 
entangled with the precipitate. The soluble milk sugar is then 
determined in the supernatant liquid from the weight of copper 
it will reduce from Fehling's solution. 

Apparatus. — 500 c.c. graduated flask, 10 c.c, 25 c.c. and 
50 c.c. pipettes, carbon filter tube, rubber-stoppered filter flask, 
suction pump, 50 c.c. 'graduated cylinder, balance and weights, 
Bunsen burner, tripod, 400 c.c. beaker, burette, air oven, stirring 
rod, wash bottle, desiccator. 

Reagents. — Fehling's solution (A. Dissolve 34.639 grams 
of copper sulphate CuSO^oHoO in water, then dilute to 500 c.c. ; 
B. Dissolve 173 grams of Rochelle salt and 125 grams of K (OH) 
in water and dilute to 500 c.c, use equal volumes of A and B, 
N/2 Na(OH), distilled water. 

Details of Procedure. — Measure into the 500 c.c. flask by 
means of a pipette, 25 c.c. of milk, the specific gravity of which 
is known. Dilute to about 400 c.c. with distilled water. Add 
10 c.c. (pipette) of copper sulphate solution ("A" solution of 
Fehling's. See above). Now add from a burette, 8.8 c.c. of 
N/2 Na(OH) solution. The solution should still retain an 
acid reaction. Dilute to the mark, mix well and allow to settle. 

Prepare a Gooch crucible. (See Instructor.) Dry the 
Gooch in an air oven heated to 100 degrees. Cool in a desiccator 
and weigh. 

Filter a quantity of the liquid containing the milk sugar 
into a dry beaker. Reject the first 100 c.c. 

Place 50 c.c. of the mixed Fehling's solution (equal volumes 
of A and B in the 400 c.c. beaker and heat to boiling on the 
tripod. To the boiling solution, add 100 c.c. of the clear filtered 
solution containing the milk sugar. Boil for precisely six min- 
utes. Filter immediately through the Gooch, wash two or three 



38 

times by decantation with hot water, then transfer the entire 
precipitate to the Gooch. Remove the water by washing with 
alcohol and the alcohol by washing with ether. Dry in an air 
oven (after the odor of ether is gone) at a temperature not ex- 
ceeding 100 degrees C. Cool in a desiccator and weigh. 

Calculation of Results. — By means of the tables in Bul- 
letin 107, Bureau of Chemistry, pages 48-49, find the equivalent 
of the CuoO in terms of lactose, then: 

Per cent, lactose = (weight of lactose) X 5 X 100/25 (spe- 
cific gravity). 

7. Determination of Total Nitrogen. 

Principle of the Method. — Milk is digested with con- 
centrated sulphuric acid until all the nitrogenous substances are 
converted to ammonium sulphate and the ammonia subsequently 
distilled out with Na(OH) and caught in a measured excess of 
acid of known strength. 

Apparatus. — Kjeldahl digestion flask and distillation ap- 
paratus, Bunsen burner, tripod, iron stand, clamp, burette, pipette 
(5 and 10 c.c), Erlenmeyer. 

Reagents. — C. P. H0SO4 specific gravity 1.84, saturated 
Na(OH), N/10 H,SO„ N/10 Na(OH) or K(OH), powdered 
K2SO4, phenolphthalein. 

Details of Procedure. — Place in the Kjeldahl digestion 
flask 5 c.c. of milk (pipette). Add 10 grams of powdered 
potassium sulphate, then 20 c.c. cone, sulphuric acid. Digest 
over a, small flame until the danger from foaming has passed, 
then raise the temperature till the acid is boiling and continue 
the heating until the contents of the flask are light straw-colored 
or colorless. Cool, add about 250 c.c. of distilled water. Add a 
little phenolphthalein and two or three pieces of pumice. 

Assemble the apparatus, putting 50 c.c. (pipette) N/10 
H2SO4 in the absorption flask. Add 50 c.c. saturated Na(OH) 
to the Kjeldahl flask. (The solution in the flask should be 
strongly alkaline.) Immediately replace the stopper and make 
sure that all joints are tight. Heat cautiously, finally raising 
to the boiling and continue until all the ammonia has passed over 
or until the bulb of the receiver is filled with liquid. 



39 

Remove the receiver, add methyl-orange and titrate the ex- 
cess of H.SO^ with N/10 K(OH) or Na(OH). 

Calculation of Result. — 
1 c.c. N/10 H.SO^ = .014 grams nitrogen. 

= .014 X 100/15.7 (since protein contains 

15.7 per cent. N). 
= .014 X 6.38. 
Per cent, protein = V X .0839 X 100/5 (specific gravity), 
where "V" is the volume of N/10 acid neutralized by the am- 
monia. 

8. Detection of Added Water (Zeiss Dipping Refractometer), 

Principle of the Method. — When light enters a medium 
in which its velocity is either increased or diminished, the light 
is bent or refracted. A definite pair of substances produces a 
definite effect, that it has a constant refractive index. 

Pure milk serum has a refractive index ranging from 40 to 
42.5 on the arbitrary scale of this instrument. Added water 
lowers the refractive index. 

Apparatus. — Zeiss immersion refractometer, thermometer, 
beaker, filter paper. 

Reagents. — Twenty-five per cent, acetic acid (specific grav- 
ity 1.035). 

Details of Procedure. — To 100 c.c. of milk, at a tempera- 
ture about 20 deg. C, add 25 c.c. of the acetic acid and heat 
in a covered vessel on a water bath for twenty minutes at 70 
degress C. Place the beaker in ice water for ten minutes and 
separate the curd from the serum by filtering through a dry 
paper. Transfer about 35 c.c. of the serum to one of the beakers 
of the Zeiss apparatus, adjust the temperature to "exactly 20 
degrees and take the refractometer reading. 

Note. — A reading below 39 indicates added water, between 
39 and 40, the sample is to be considered suspicious. 

g. Detection of Formaldehyde. 

Principle of the Method. — Milk containing formalin when 
heated with hydrochloric acid containing a trace of ferric 
chloride gives a characteristic violet color. 

Apparatus. — Twelve cm. casserole, Bunsen burner. 



40 

Reagents. — Concentrated HCl, containing FeCl.; in the pro- 
portion of 3 c.c. of a 10 per cent, solution of ferric chloride per 
liter. 

Details of Procedure. — Place 10 c.c. of the milk to be 
tested in a casserole and add an equal quantity of the hydrochloric 
acid. Hold the casserole over a small flame of the Bunsen 
burner and heat slowly, almost to boiling. During the heating, 
give the casserole a rotary motion in order that the curd when 
formed, will be broken up. The presence of formaldehyde will 
be indicated by the formation of a violet coloration. 

Note. — If the curd acquires a pink color immediately upon 
the addition of the acid, an azo dye is indicated (q. v.). 

In making this test, first use a sample to which a trace of 
formalin has been added. 

The use of formaldehyde can never be justified. 

10. Detection of Boric Acid. 

Principle of the Method. — Turmeric paper, wet with a 
solution of boric acid, gives, upon drying, a rose pink colora- 
tion. 

Apparatus. — Nine cm. casserole, Bunsen burner, tripod, 
water bath, filter stand, two-inch funnel. 

Reagents. — Turmeric paper, ammonium hydroxide, hydro- 
chloric acid. 

Details of Procedure. — Place 5 c.c. of milk in the cas- 
serole, make distinctly alkaline with Na(OH) and evaporate to 
dryness on the steam bath. Destroy the organic matter by igni- 
tion. Add 10 to 15 c.c. of water to the ash, then HCl, drop by 
drop, until the liquid is acid. Filter. Dip a strip of turmeric 
paper into the filtrate and dry on the outside of a test tube in 
which water is being boiled. A rose red color indicates boric 
acid. Ammonium hydroxide turns the paper dark green. Heat- 
ing restores the original color. 

Questions. — Why is it necessary to add the Na(OH) be- 
fore the evaporation? 

Why acidify the ash with HCl? 

Does the change to dark green from the rose red turmeric 
paper, upon the addition of ammonium hydroxide, make this 



42 

If the curd is perfectly white, azo dye and caramel are 
absent. The color, if any, must be annatto. 

a. Annatto is present. 

Evaporate the ether solution and treat the residue with dilute 
Na(OH) solution. Pour the liquid on a wet filter paper. The 
fat is caught on the paper, while the annatto dyes it. Wash the 
fat from the paper with a stream of hot water. Allow the paper 
to dry. Annatto, if present, will impart an orange color to the 
paper. Add a few drops of SnCL and it becomes pink in the 
presence of annatto. 

b. Azo dye. 

If the extracted curd is colored, add cone. HCl to a portion of 
it. If azo dyes are present, the curd becomes pink. 

c. Caramel. 

If the extracted curd has a brown color and neither azo 
dyes nor annatto are found, we may assume the presence of 
caramel. 
Confirmatory test for caramel. 

To 100 c.c. of milk, add an equal volume of alcohol and 
filter. Any caramel is in the whey. Add a solution of basic 
lead acetate and filter. Dry the precipitate (exclude all H^S) 
and if the precipitate is then either white or pale straw color, 
caramel is absent; if more or less brown, caramel is present. 

Note. — Azo dyes are more frequently used for this purpose 
than either of the other two. 

12. Examination of Sediment in Milk. 

Fill two sedimentation tubes with a sample of common milk. 
Whirl a few minutes in a centrifuge. If sufficient sediment is 
not obtained, decant the milk carefully, fill again with milk 
and whirl again. Repeat till sufficient sediment is obtained to 
permit of its macroscopic and microscopic examinations. Place 
on a slide and examine. 

13. Development of Acidity. 

Prepare six clean sterilized Erlenmeyer flasks. Add to each 
50 c.c. of a sample of common milk with a sterilized pipette. 
Stopper each flask with cotton and titrate them successively with 
N/10Ba(OH)^ and phenolphthalein at intervais of not less than G 



43 

hours. Plot a curve showing the acidity as a function of the 
time. 

14. Volatile Acids Developed on Souring. 

Proceed the same as in the development of the acidity up to 
the point of titration. At this point acidify with sulphuric acid 
(see volatile acids in butter, p. 46 ), and distil ofif the volatile 
acids. Titrate with N/10Ba(OH)o. 

Plot the quantity of volatile acids produced as a function of 
the time. 

Some Practical Questions. — 1. What might you infer if 
two samples of milk should have the specific gravities: (a) 1036, 
(b) 1025? What other inference might be drawn from milk 
having a specific gravity of 1025? 

2. What significance has low total solids? 

3. What would you conclude if analysis showed : 

(a) Total solids low, the ratio of solids not fat to fat 
about the same as in normal milk? 

(h) Total solids and fat low, while solids not fat about 
normal ? 

(c) Total solids low, solids not fat materially reduced, and 
the ratio of solids not fat to fat also proportionately reduced? 

C. EXAMINATION OF BUTTER. 

I. Sampling. 

If a large amount of butter is to be tested, the method by 
which the sample is obtained is of vast importance. To obtain 
a uniform sample, take a large number of small quantities from 
various parts of the butter until from 100 to 500 grams, accord- 
ing to the original bulk, are obtained. Add the portions together. 
Save a sample for microscopic examination. Melt the remainder 
of the sample in an Erlenmeyer at the lowest possible tempera- 
ture. Allow the mass to cool. During the cooling, stopper the 
flask and shake it until it is sufficiently cool to prevent the 
separation of water and fat. Pour the butter into an Erlen- 
meyer so small that it just holds the sample. Stopper and then 
put in a cool place until needed. 



44 

2. Determination of Moisture, 

Principle of the Method. — A sample of butter is heated 
to a temperature of boiling water until all the moisture is volatil- 
ized. The quantity is determined by the loss in weight. 

Apparatu.s. — Aluminum dish (9 cms.), balance and weights, 
steam bath, desiccator. 

Details of Procedure. — Accurately weigh the aluminum 
dish. Place about three grams of butter in this dish and weigh 
again. Heat the dish on the steam bath for one hour, dry it, 
cool in a desiccator, then weigh. Repeat the heating for another 
half hour, dry cool and weigh once more. Repeat the operation 
until two consecutive weighings show no change in weight. 

Calculation of Results.— Express the loss of weight as 
per cent, of water. 

Note. — Keep the material in the aluminum dish for the "De- 
termination OF Fat." 

3. Determination of Fat. 

Principle of the Method. — The method depends upon the 
fact that fat alone is dissolved from dry butter by anhydrous 
ether. 

App.j^ratus. — The aluminum dish containing the residue 
from the Determination of Moisture, Gooch crucible, small 
wash bottle containing anhydrous ether, oven, desiccator, balance 
and weights. 

Reagents. — Anhydrous ether. 

Details of Procedure. — Treat the weighed contents of the 
aluminum dish with pure anhydrous ether. Pour all the wash- 
ings through a dried and weighed Gooch, and finally transfer 
all the material to the Gooch. Wash the contents of the Gooch 
with ether till free from fat, then dry the crucible (after the odor 
of ether has disappeared), in an air oven at 100 degrees. Re- 
peat the drying till the weight is constant. 

Calculation of Resl^lts. — The loss in weight upon ex- 
traction with ether is the weight of fat. 

Per cent. Fat = 100 (weight of fat)/(weight of butter). 

Note. — Keep the Gooch and contents for the determination 
of ash. 

Caution. — Be sure that no flames are in the vicinity when us- 
ing ether. It boils at 37 degrees C and its vapor is inflammable. 



45 

4- Determination of Casein and Ash. 

Principle of the Method. — The residue from the fat ex- 
traction which contains only casein and mineral matter is ignited. 
The casein is first carbonized, then the mass is incinerated, where- 
upon the casein is entirely consumed, leaving the mineral matter. 

Apparatus.^ — Tripod, Bunsen burner, crucible and residue 
from fat extraction, desiccator, balance and weights. 

Details of Procedure. — Cover the Gooch crucible contain- 
ing the residue from the fat determination and heat carefully 
with a small flame, gradually increase the heat to a temperature 
just below redness. Remove the cover and continue the heating 
at the same temperature till the contents of the crucible are 
perfectly white. Cool in a desiccator and weigh. 

Calculation of Results. — Per cent, casein = 100 (loss on 
ignition) /(weight of butter). Per cent, ash = 100 (weight of 
ash) /(weight of butter). 

5, Determination of Salt. 

Principle of the Method. — The salt is extracted from the 
butter by repeatedly washing the sample with hot distilled water. 
The quantity of salt in the aqueous solution is determined vol- 
umetrically with silver nitrate. 

Apparatus. — Beakers, 1-100, 1-400 c.c, separatory funnel, 
wash bottle with boiling water, burette, stirring rod, pipettes, 
1-10, 1-25 c.c, 1-250 c.c. graduated flask. 

Reagents. — N/10 silver nitrate, potassium chromate solu- 
tion. 

Details of Procedure. — Weigh the 100 c.c. beaker accu- 
rately to the nearest centigram. Add from 5 to 10 grams of 
butter and weigh again. Add about 25 c.c. of boiling water and 
pour into the separatory funnel. Shake well and then allow to 
separate. Draw off the water into the 250 c.c. graduated flask 
and repeat the extraction with water till the graduated flask is 
almost filled to the mark. Cool the flask and the contents to 
room temperature, adjust to the mark with distilled water and 
mix thoroughly. 

Take 10 c.c. of the salt solution in a beaker, add about 1 
c.c. of KXrO^ solution and titrate with N/10 silver nitrate solu- 
tion to the production of a faint red tint in the place of 
the pure yellow color of the solution. From this prelimi- 



46 

nary trial, determine the most suitable volume of the salt 
solution that should be taken to yield an accurate result. 
Measure into the 400 c.c. beaker the determined volume of 
salt solution, add 1 c.c. of potassium chromate solution and 
titrate as before, remembering that the tendency is to overshoot 
the mark by adding too much silver nitrate solution ; stop at the 
first departure from the pure yellow color. Make a duplicate 
titration if the quantity of the salt solution permits. 

Calculation of Results. — Per cent, salt = 100 (c.c. N/IO 
silver nitrate per 250 c.c. salt solution X .00585) /(Grams of 
butter ) . 

NoTR. — Salt usually present varies from 0.5 to 0.7 per cent. 

6. Examination of the Melted Fat. 

Principle of the Method. — When fat is melted at a tem- 
perature of 50 degrees C, that separating from fresh genuine 
butter is clear, while that from process or renovated butter or 
oleo is more or less turbid. This is due to the fact that these latter 
fats contain a certain proportion of milk that has not been elimi- 
nated in the manufacture. 

Details of Procedure. — Observe the above in the prepara- 
tion of the butter fat (q. v.). 

7. Preparation of Butter Fat for Examination. 

NoTi':. — This may be done by one student preparing sufficient 
of the fat for the whole class. 

Melt the butter (10 grams per student if working singly) 
in a sufficiently large test tube, heated in a bath of water at 50 de- 
grees for two or three hours, until the water and curd have entirely 
separated from the fat. Pour the clear supernant fat through a 
dry filter paper. Keep the aqueous liquid at the bottom of the 
tube for the detection of boric acid, (q. v.). See "Examination 
OF the Melted Fat" (q. v.). 

8. Determination of Volatile Acids. 

Principle of the Method. — The butter fat is saponified 
with sodium hydroxide, the soap thus formed decomposed with 
sulphuric acid, liberating the free fatty acids. The volatile acids 
are then separated from the fixed acids by distillation and meas- 
ured by titrating the distillate with standard barium hydroxide. 



47 

Apparatus. — Erlenmeyer flask, 8 oz, distillation apparatus, 
receiver graduated at 110 c.c, Bunsen burner, tripod, wire gauze, 
funnel, burette, stirring rod, pipettes 25 c.c. and 100 c.c. 

Reagents. — Standard barium hydroxide approximately N/10 
hydrochloric acid, sulphuric acid 1-5, glycerol-soda solution (20 
c.c. of a solution of NaOH, 1 gram solid to 1 c.c. of water,- plus 
180 c.c. glycerol, pumice, phenolphthalein ( 1 per cent, alcoholic 
solution). 

Details of Procedure. — Weigh the Erlenmeyer flask to the 
nearest centigram. Add about 5 grams of fat prepared as di- 
rected above and weigh again to the nearest centigram. Measure 
into the flask 20 c.c. of the glycerol soda solution and heat the 
flask over the Bunsen flame till the fat is completely saponified ; 
complete saponification being indicated by the contents becoming 
homogeneous, and bright and clear. Allow to cool and add 135 c.c. 
cold distilled water, avoiding the production of foam. When the 
soap has entirely dissolved, add 5 c.c. of the dilute sulphuric 
acid (1-5). Add a few pieces of pumice and distil regularly, so 
that 110 c.c. are collected in one half hour. 

During the distillation, place the clear barium hydroxide 
solution in a burette. Place 25 c.c. N/10 HCl in a beaker, dilute 
slightly with water, add phenolphthalein and drop in the barium 
hydroxide till the end point is obtained. Repeat several times 
till the results are concordant. This standardizes the barium 
hydroxide. 

Mix the distillate thoroughly, filter if necessary from any 
solid particles, take 100 c.c. of the clear liqvnd by means of a 
pipette and titrate with the standardized barium hydroxide, using 
0.5 c.c. phenolphthalein as indicator. 

Carry out a blank determination with the reagents, i. e., go 
through the operations above described, omitting the butter fat. 

Calculation of the Result. — 
Reichert-Meissl number = c.c. N/10 alkali required by volatile 

acids from 5 grams of fat. 
= (c.c. N/10 Ba(OH)2 X 1.1 XV 
(weight of fat). 

Note. — The U. S. standard butter fat has a Reichert-Meissl 
number not less than 24. Oleomargarine or butterine has a Reich- 
ert-Meissl ranging from 0.5 to 5.5. This test is therefore used 



48 

to detect the presence of foreign tissue fat in butter. 

9. Detection of Boric Acid. 

Principle of the jNIethod. — The borax or boric acid is to 
be found in the aqueous liquid that separates from the butter 
on melting. The boric acid is then detected by the turmeric paper 
test as described under milk (q. v.). 

Apparatus.^ — Test tubes, casserole. Bunsen burner. 

Reagents. — Same as under milk. 

Details of Procedure. — Take the aqueous liquid which 
separates in the preparation of the fat. q. v., and ap])ly the test 
as described under milk. 

10. Detection of Glucose. 

Principle of the Method. — The soluble glucose is ex- 
tracted from the butter by repeatedly washing with hot water, 
and its presence in the aqueous solution detected by means of 
Fehling's solution. ( See the determination of lactose in milk. ) 

Apparatus. — Beakers. l-l(MH) and 1-400 c.c. separatory 
funnel, wash bottle, tripod and burner. 

Reagent. — Fehling's solution. 

Details of Procedure. — Place 10 to lo grams of butter in 
a small beaker. Pour a quantity of boiling water over the sample 
and when melted, pour into the separatory funnel. Shake, allow 
to separate, draw ofif the aqueous layer, heat to boiling and add 
Fehling's solution. A yellow or red precipitate indicates the 
presence of glucose. 

Question. — How could the above procedure be made quanti- 
tative? 

11. Foam Test. 

Principle of the Method. — An unmelted fat, such as 
butter, foams when heated over a flame, whereas those that have 
been melted, such as lard, sputter noisily when so heated. 

Apparatlts. — Two small evaporating dishes, pjunsen burner, 
tripod. 

Details of Procedure. — Heat three or four grams of butter 
in a small evaporating dish over a free Bunsen flame and note 
whether the fat foams quietly or sputters and crackles noisily. 
Repeat using a small quantity of oleomargarine or process butter. 

Note. — This test mav readilv be carried on in the kitchen bv 



49 

substituting a spoon for the evaporating dish and the flame of 
the gas stove for the burner. 

12. Microscopic Examination of Butter, Process Butter and 

Oleo. 

Principle of the Method. — Fats that have been melted con- 
tain crystals of fat, those which have not as butter are non- 
crystalline. Crystallinity can be detected by the effect of the 
material on polarized light, crystalline bodies giving a parti- 
colored field, while non-crystalline bodies give a uniform field. 

Apparatus.— Microscope with polarizing attachment, slides, 
cover glasses. 

Details of Procedure. — Place a small amount of the sample 
to be tested on a clean glass slide, press a cover glass over the 
fat and examine under the microscope with polarized light. Re- 
peat, using samples of oleo, lard or beef drippings. 

13. Detection of Artificial Coloring. 

Note. — The artificial coloring of butter is quite common and 
is permitted by the laws of all the states. 

At the present time, annatto and oil soluble azo dyes are 
practically the only colors used, 
(a) Detection of annatto. 

Principle of the Method. — The solubility of annatto in 
sodium hydroxide and the ability of filter paper to absorb the 
color from this solution are the principles upon which this detec- 
tion depends. The final verification of annatto is by the reaction 
of stannous chloride upon it. 

Apparatus. — One hundred c.c. beaker, fimnel, filter paper. 

Reagents. — Fat, dilute solution of sodium hydroxide, stan- 
nous chloride. 

Details of Procedure. — Treat two or three grams of the 
melted and filtered fat (freed from salt and water) with warm 
dilute sodium hydroxide and after stirring, pour the mixture 
upon a warm wet filter, using to an advantage a hot funnel. If 
annatto is present, the filter will absorb the color so that when 
the fat is washed ofif by a gentle stream of water, the paper will 
be dyed straw color. It is well to pass the warm alkaline filtrate 
two or three times through the fat on the filter to insure removal 



50 

of the color. If after dyeing the fiUer, the color turns pink on 
the appHcation of stannous chloride solution, the presence of 
annatto is assured, 
(b) Detection of azo colors {Geisler's method). 

Principle of the AIethod. — Azo dyes will produce a pink 
or violet red coloration upon some varieties of fuller's earth. 

Apparatus. — Porcelain plate. 

Reagent. — Fuller's earth. 

Details of Procedure. — Spread a few drops of the clarified 
fat upon the porcelain plate and add a pinch of fuller's earth. 
In the presence of various azo dyes, a pink to violet red colora- 
tion will be produced in a few minutes. 

Note. — Some varieties of fuller's earth react much more 
readily than others, in fact, some do not react at all. It is, there- 
fore, essential that the fuller's earth be previously tested. 

D. OLIVE OIL. 

I. Detection of Cottonseed Oil in Olive Oil. 

Object of the Experiment. — To test an unknown sample 
of olive oil by the Bechi and Halphen methods in order to detect 
adulteration by the addition of cottonseed oil. 

Apparatus. — Test tubes, beaker, tripod, Bunsen burner. 

Reagents. — Bechi's reagent, prepared by dissolving 2 
grams of silver nitrate in 20 c.c. of 95 per cent, alcohol free from 
aldehyde, adding 40 c.c. of ether and then made slightly acid with 
nitric acid. 

Halphen's reagent is a mixture of equal volumes of amyl alco- 
hol and carbon disulphide in which 1 per cent, of sulphur has been 
dissolved. 

Details of Procedure.— (a) Bechi's test (Hehner's modi- 
fication). 

Mix a small amount of the oil in a test tube with half its 
volume of Bechi's reagent and immerse the tube in boiling water 
for fifteen minutes. The presence of cottonseed oil is indicated 
by darkening due to reduction of silver. 

Halphen's test: Mix in a test tube a small quantity (5 to 10 
c.c.) of the oil with an equal volume of Halphen's reagent. 



51 

Loosely stopper the tube with cotton and heat for fifteen minutes 
in a bath of saturated brine. A deep red or orange color shows 
the presence of cottonseed oil. 

Note. — Heat a sample of cottonseed oil to a temperature of 
250 degrees for ten minutes and then apply Halphen's test. ( ?). 

2. The Effect of Light in Increasing the Acidity. 

Object of the Experiment. — Samples of olive oil are 
exposed to sunlight and the acidity is determined after exposures 
of different intervals. 

Apparatus. — Four glass-stoppered bottles 150 to 200 c.c. 
capacity, burette, 50 c.c. pipette. 

Reagents. — Alcohol (neutral), phenolphthalein, N/10 
Na(OH) or K(OH). 

Details of Procedure. — (a) By means of the pipette meas- 
ure into each of the four bottles 50 c.c. of the oil to be examined. 
Give the pipette ample time to deliver the total 50 c.c. Record 
this. Allow the same period for drainage each time the pipette 
is used to deliver a sample of oil. Stopper each of the bottles 
and set them in the sunlight. 

(b) Measure 50 c.c. of the oil (pipette) into a beaker, then 
add 50 c.c. of neutral alcohol. Add 10 to 15 drops of phenol- 
phthalein and titrate with N/10 alkali. Record the result. 

(c) After one week's time remove the stopper from one of 
the bottles, add 50 c.c. of neutral alcohol, 10 to 15 drops of 
phenolphthalein and titrate as before with N/10 alkali. Record 
the result. 

(d) After an interval of two weeks repeat "c" with a second 
bottle. At three weeks' time determine the acidity of a third, and 
at the end of four weeks repeat the same with the last sample. 
Record the results. 

Calculation of the Results. — Record the acidity in terms 
of c.c. of N/10 acid per 100 c.c. of oil, also in grams of oleic acid 
per 100 c.c. of oil. 

Question. — How would you proceed in order to determine 
the per cent, by weight of oleic acid ? 



52 

E. INSPECTION OF FLOUR. 

1. Cold Water Extract. 

Details of Procedure.— Weigh out on the flat scales 100 
grams of flour. Transfer it to the graduated liter flask and thor- 
oughly mix it with distilled water. Finally make up to the mark, 
stopper the flask, mix thoroughly by shaking frequently during 
one of the laboratory periods. Allow to stand over night. 

Weigh the porcelain dish to the nearest milligram. Measure 
into the weighed dish by means of a pipette 50 c.c. of the cold 
water extract and evaporate to dryness on the steam bath. Dry, 
cool in a desiccator and weigh to the nearest milligram. Repeat 
the lieating until two successive weighings show no alteration in 
weight. 

Calculation of Result. — Per cent, cold water extract = 
residue from 50 c.c. of the filtrate multiplied by 20. 

Note. — According to Wanklyn the cold water extract from 
a sound flour should not exceed 5 per cent. 

The extract should not stand longer than 24 hours, as 
fermentation sets in and butyric acid is formed. 

Question.- — 1. Of what value is this determination? 

2. Determination of Gluten (Wiley). 

Principle of the METHon. — The flour is first made into a 
dough from which the starch and soluble material is waslied out, 
leaving the gluten. 

Apparatus. — Porcelain dish (8 cms.), aluminum dish, spat- 
ula, steam bath, balance and weights, desiccator. 

Details of Procedure. — Weigh to the nearest centigram 
about 10 grams of flour. Transfer the weighed sample to a 
porcelain dish, add not more than 10 c.c. of water and then by 
use of a spatula work the mass up into a small ball, taking care 
not to allow any of the material to adhere to the sides of the dish. 
Allow the ball of dough to stand for one hour. 

After standing knead the ball of dough in the hand under a 
small stream of water from the spigot until all the soluble 



53 

material and starch has been removed. Place the ball of gluten in 
cold water and allow to remain for one hour. 

Accurately weigh an aluminum dish. 

Remove the ball of gluten from the water, press it between 
the fingers until it is as dry as possible, then roll it into a small 
ball, place it in the weighed aluminum dish and weigh. Record 
the weight as moist gluten. Now place the dish and contents on 
the steam bath for twenty-four hours, then dry, cool in a desic- 
cator, weigh and record the weight as dry gluten. 

Calculation of the Result. — Per cent, gluten = 100 
(weight of gluten) /(weight of sample). 

Note. — Gluten is composed of two proteids, glutenin and 
gliadin. Wheat flour contains from 9 to 13 per cent, gluten. 

3. Detection of Artificial Bleaching. 

Note. — The artificial bleaching of flour consists in adding a 
small amount of nitrogen peroxide to the flour, which renders 
the yellow oil present nearly colorless. 

(a) Gasoline Method. 

Principle of the Method. — Gasoline dissolves the oil in 
the flour. The color of the oil is determined by observing the 
tint given to the solvent by the dissolved material. 

Apparatus. — Glass-stoppered bottle (4 oz.). 

Reagents. — Pure gasoline. 

Details of Procedure. — Place about 20 grams of flour in 
the glass-stoppered bottle, then nearly fill it with gasoline. Shake 
well and allow the contents to settle. The gasoline from an 
unbleached flour so treated will have a distinct yellow color, while 
that from a bleached flour will be almost colorless. 

Note. — Conduct a similar experiment on a flour known to be 
unbleached and compare the result. 

(b) Sulphanilic Acid — Alpha Napththylamine Method. 
Principle of the Method. — When sulphanilic acid [C^H^ 

(NHy) (HSO3)] and a-naphthylamifie hydrochloride [Ck, H^ 
H3 NPL HCl] react in the presence of nitrous acid we have 
formed the red compound, azo benzene-naphthylamine sulphonic 
acid [CeH, (HSO,) N = NC^o H, H, NH,]. The reaction is of 
extreme delicacy. 



54 

Apparatus. — Glass-stoppered bottle (4 oz.). 

Reagents. — 1. Sulphanilic acid solution prepared by dis- 
solving 0.5 grams of sulphanilic acid in 150 c.c. of dilute acetic 
acid (about 20 per cent.). (Keep well stoppered.) 

2. Alpha naphthylamine hydrochloride solution made by dis- 
solving 0.2 grams of alpha naphthylamine hydrochloride in 20 c.c. 
of glacial acetic acid and adding 130 c.c. of 20 per cent, acetic 
acid to it. (Keep well stoppered.) 

3. Pure distilled water containing no nitrites. 

Details of Procedure. — First make a preliminary test to 
determine the purity of the water to be used in the determination. 
Almost fill the glass-stoppered bottle with the water to be exam- 
ined. Mix .equal volumes of the solutions (1) sulphanilic acid 
and (2) alpha naphthylamine hydrochloride and then add 10 c.c. 
of the mixed reagent to the water. Stopper the bottle, shake well 
and allow to stand for twenty minutes. If at the end of that 
time the solution remains colorless or turns only a very faint pink, 
the water is suitable for this purpose. 

Place a heaping teaspoon ful of flour in the clean glass- 
stoppered bottle, nearly fill it with the pure water, add 10 c.c. of 
the mixed reagent, stopper, shake and allow to settle. 

After twenty minutes observe. 

A bleached flour will impart a tint to the solution varying 
from a pink to a deep red. depending upon the degree of the 
bleaching. Unbleached flour should give no more color than that 
imparted by the water itself. 

Note. — The test should be accompanied by one made on flour 
known to be unbleached and the results compared. 

Question. — What is the eflfect upon the finished loaf when 
bleached flour is used in the preparation? 

4. Determination of Total Carbohydrates. 

Principle of the Method. — Hydrolyze the carbohydrates 
with dilute acid whereby the starch is converted to sugar. Deter- 
mine the quantity of sugar by Fehling's reagent. 

Apparatus. — Erlenmeyer, condenser, 500 c.c. graduated 
flask, 25 c.c. pipette. 

Reagents. — Hydrochloric acid (Sp. Gr. 1.125), Fehling's 
solution ("A" and "B"). 



55 

Details of Procedure. — Accurately weigh about three 
grams of the sample. Transfer the same to an Erlenmeyer, add 
200 CO. of a mixture of 180 c.c. of water and 20 c.c. of hydro- 
chloric acid (1.125), connect with a reflux condenser and boil 
for an hour and a half. 

While this boiling is in progress, prepare a Gooch crucible, 
washing it successively with water, alcohol and ether, and then 
drying at 100 degrees, cooling in a desiccator and weighing. 

After the carbohydrates have been refluxed for the time 
stated, cool, neutralize with Na(OH), transfer to the 500 c.c. 
graduated flask and make up to the mark with distilled water. 
Mix well and filter a portion into a dry beaker. 

Sixty c.c. of the mixed copper reagent are diluted with fiO 
c.c. of water and heated to boiling. Add 25 c.c. (pipette) of the 
dextrose solution and boil 2 minutes. Filter immediately through 
the Gooch. Wash successively with water, 10 c.c. of alcohol and 
10 c.c. of ether. After the odor of ether has vanished dry at 
100 degrees for one-half hour. Cool in a desiccator and weigh 
as Cu^O. 

Calculation of the Result. — "M" grams of Cu„0 = "P" 
grams of dextrose. (See tables U. S. Bulletin, No. 107, Dept. of 
Chemistry.) 

Per cent, starch = 100 (PX20X0.9) /(weight of sample). 

5. Action of Heat on Starch. 

Object of the Experiment. — The experiment is designed 
to show the physical and chemical reactions that take place in 
starch upon the application of heat. 

App.\ratus. — Test tubes, evaporating dish, Bunsen burner, 
oven, beakers, tripod. 

Reagents. — Water, Fehling's solution, tincture of iodine or 
iodine dissolved in potassium iodide solution, nitric acid, starch. 

Details of Procedure.— (a) To one gram of starch in a 
small beaker add 50 c.c. of cold water. Filter, and if necessary 
repeat several times until the filtrate is perfectly clear, and apply 
the test for starch in (B). What is the solubility of starch in 
cold water? 

(b) Make a paste by rubbing a gram of starch with a very 
small quantity of water. Slowly add to the paste a small quantity 



56 

at a time to 200 c.c. of boiling water and stir after each addition. 
Cool. ( ?). Test for starch by adding to a portion of the above 
clear liquid a few c.c. of tincture of iodine or of iodine dissolved 
in potassium iodide solution. A deep blue color indicates the 
I)resence of starch. 

To another portion of the starch solution add mixed Fehling's 
solution and heat. (?). Consult an Instructor if necessary. 

(c) Place about 20 grams of starch in a porcelain evapo- 
rating dish. Heat cautiously to a temperature of 210 to 280 
degrees C. for one-half hour, stirring constantly. Cool. Place a 
pinch of the material in a test tube and try its solubility in cold 
water. ( ?). Add alcohol to the aqueous solution. ( ?). 

Test a portion of this material for starch by the iodine test. 
( ?). Has a chemical reaction taken place? How do you know? 
What is the new material? Give its chemical formula. 

(d) Moisten ten grams of starch with dilute nitric acid. 
Dry the paste first on the steam bath and finally heat over a small 
flame from the IJunsen burner to a temperature of 110 degrees C. 
Test the material; (a) solubility, (b) iodine test, (c) Fehling's 
solution. What are vour conclusions? 

6. Action of Acids upon Starch. 

( )i!ji:cT OF THE EXPERIMENT. — Starch is treated with boiling 
acid and afterwards tested in order to determine whether a 
chemical reaction has taken place. 

Apparatus.— Erlenmeyer (S oz.), condenser, tripod. Bunsen 
burner, wire gauze, test tubes, beaker, microscope. 

Reagent.s. — Hydrochloric acid (Sp. Gr. 1.12.")), Fehling's 
solution, tincture of iodine or iodine in potassium iodifle ; sodium 
hydroxide. 

Details of PROcEnuRE. — Place about three grams of starch 
in an Erlenmeyer. add 200 c.c. of distilled water and 200 c.c. 
of the hydrochloric acid. Connect the Erlenmeyer with a reflux 
condenser and boil for half an hour. 

Disconnect the apparatus, remove about 10 c.c. of the solu- 
tion, cool under running water, neutralize with Na(OH), and 
applv the test for starch. If this test proves positive connect up 



57 

the apparatus and boil for another half hour. Repeat if necessary 
until iodine gives no indication of starch. 

Neutralize a portion of the solution with Na(OH) and apply 
the Fehling's solution test. (?). 

Evaporate a portion of the liquid on a large clock glass on 
the steam bath. Examine the residue under the microscope. Is 
it starch ? 

Questions. — 1. What change has taken place in the starch? 

2. Write the reaction for the change, remembering that it is 
a case of hydrolysis. 

3. How could the principle of this experiment be applied for 
the quantitative determination of starch in some of the commer- 
cial material? 

7. Conversion of Starch to Dextrose by Diastase. 

PRiNCirLE OF THE METHOD. — The enzyme diastase found in 
malt extract converts starch into maltose and dextrin. 

Apparatus. — Beaker, test tube, thermometer Erlenmeyer, 
stirring rod. 

Reagents. — Tincture of iodine or a solution of iodine in 
potassium iodide, Fehling's solution, malt extract or diastase pre- 
pared by one of the following methods : 

(a) Digest pulverized malt for several hours with enough 
alcohol to cover it. Filter and set the solution aside until the 
alcohol evaporates, then dissolve the residue in water. This solu- 
tion contains the diastase. 

(b) Dry malted barley may be readily obtained from any 
brewery. Treat 15 to 20 grams of the freshly pulverized malt 
for several hours with 100 c.c. of water, shaking occasionally. 
Filter the solution and add two or three drops of chloroform to 
prevent the growth of fungi. 

Detah.s of Procedure. — Treat three grams of starch in an 
Erlenmeyer with 50 c.c. of water. Immerse the flask in a beaker 
containing boiling water and stir the contents of the flask until 
they gelatinize. Cool to about 60 degrees C. and add 20 to 40 c.c. 
of the malt extract, and again immerse in a beaker containing 
water at 55 to 60 degrees. Test after a half hour for unconverted 
starch. (?). Repeat the digestion until all the starch has been 
converted to sugar. (?). Test with Fehling's solution. 



58 

F. BREAD. 

1. Determination of Moisture. 

Details of Procedure. — Weigh an aluminum dish to the 
nearest milHgram. Add about 10 grams of the finely divided 
sample and weigh again. Heat in an air oven at 100 degrees for 
one hour and re-vveigh. Repeat the heating for half an hour or 
until after two successive heatings there is no change in weight. 

Calculation of Result. — Per cent, moisture ^ 100 (Loss 
of weight by volatilization )/( Original weight taken). 

Note. — In the best samples of bread the moisture content 
varies from 33 to 40 per cent. A moisture content over 40 per 
cent, is considered objectionable. 

Perform this experiment on a sample of fresh bread, then 
repeat it when the bread has become stale. Compare the results. 

2. Acidity. 

Apparatus. — Mortar and pestle, burette. 

Reagents.— Phenolphthalein, N/10 Na(OH) or KOH. 

Details of Procedure.— Weigh 10 grams of the sample to 
the nearest centigram. Transfer to a mortar and macerate with 
100 to 150 c.c. of distilled water. Wash oft' the adhering particles 
from the pestle by a stream of water from the wash bottle. Add 
two or three drops of phenolphthalein and titrate with N/10 
alkali. 

Calculation of Resui^t. — Calculate c.c. X/10 alkali per 
100 grams bread, also per cent, lactic acid. 

Note. — Procure a number of samples of bread varying in 
quality from excellent to bad and compare them as to acidity. 

Piread is seldom if ever adulterated. Adulterants found in 
bread are generally due to the use of impure flour. 

G. MOLASSES. 

Note.— Refore taking a sample of molasses for any determi- 
nation, stir thoroughly, as sugar is apt to have crystallized out. 

I. Determination of Reducing Sugar (Dextrose). 

Principle of the Method. — The determination of sugar is 



59 

made by means of Fehling's solution, the reducing sugar being 
calculated to dextrose. 

Reagents. — Fehling's solution (A and B). 

Details of Procedure. — Weigh a 100 c.c. graduated flastf. 
Place in it approximately 5 grams of molasses, weigh exactly 
and dilute slightly. If the solution is clear, continue the dilution to 
the mark ; but if cloudy, add 2 to 5 c.c. of lead subacetate before 
diluting to the mark. Filter, if necessary, through a dry paper 
and take 25 c.c. of the clear liquid. Place in a 100 c.c. graduated 
flask. This flask now contains one-fourth of the original sample. 
In case lead acetate has been used, add sodium sulphate in suf- 
ficient amount to precipitate all the lead. Dilute to the mark, 
filter if necessary. 

Place 30 c.c. of the "A" solution of Fehling's and 30 c.c. of 
"B" into a beaker containing 60 c.c. of distilled water and heat 
to boiling. Add 25 c.c. (pipette) of the prepared sample con- 
taining one-sixteenth of the original weight and boil for two 
minutes. Filter immediately through a Gooch previously washed 
with water, alcohol, ether, then dried, cooled in a desiccator and 
weighed. Wash the Cu^O with hot distilled water, then 10 c.c. 
of alcohol, followed by 10 c.c. of ether. Dry in an air oven, 
cool in a desiccator and weigh. 

Calculation of the Result. — From tables in the U. S. 
Bulletin, No. 107, Bureau of Chemistry, pages 50-51, obtain the 
weight of dextrose equivalent to the milligrams of Cu.O in the 
determination, then 

Per cent, dextrose = 100 (weight of dextrose 
16) /(grams molasses). 

2. Determination of Sucrose. 

Principle of the Method. — The sucrose is inverted with 
hydrochloric acid and the total sugar then determined by Fehling's 
solution. The total dextrose thus found less the dextrose found 
in the preceding experiment is calculated to sucrose. 

Reagents. — Fehling's solution ("A" and "B"). 

Details of Procedure. — Dilute an accurately weighed sam- 
ple, approximately 1 gram to 100 c.c. with distilled water. Add 
3 c.c. of concentrated HCl and heat to 70 degrees for ten minutes, 
then neutralize with Na OH and dilute to 500 c.c. 



60 

Place 30 c.c. each of "A" and "B" solutions of Fehling's in 
a beaker containing 35 c.c. of water. Heat to boiling, add from 
a pipette 50 c.c. of the sugar solution and boil for two minutes. 
From this point proceed as directed in the determination of 
dextrose. 

H. I. COLOR IN CANDY. 

Procure some samples of highly colored candy. Dissolve 
in water, acidify with hydrochloric acid and boil with pieces of 
white woolen cloth, the latter having first been cleansed by wash- 
ing in dilute alkali. 

If the wool is dyed, boil it with weak ammonia till as much 
color is removed as possible. Acidify the solution and boil with 
a fresh piece of wool. 

If this piece is dyed, we may infer the presence of coal tar 
dyes. 

PREPARATION OF NORMAL SOLUTIONS. 

A normal solution is one that contains one (1) gram-equiv- 
alent of the active radical per liter of solution. 

Thus in the case of acids, hydrogen is the active radical, so 
that to make 1 liter of normal acid we require such a weight of 
the acid as contains one gram-equivalent of hydrogen radical. 
One gram-equivalent of hydrogen radical is contained in one mol 
of hydrochloric acid in one-half mol of sulphuric acid, etc. 

In the case of bases, the active radical is (OH), so that to 
make 1 liter of a normal solution of a base we require one gram- 
equivalent of hydroxyl radical. One gram-equivalent of hydroxyl 
is contained in one mol of sodium hydroxide, in one-half mol of 
barium hydroxide, etc. 

In the case of oxidizing solutions, available oxygen is the 
active radical. Thus 1 liter of a normal oxidizing solution will 
contain eight grams of available oxygen. Reducing solutions con- 
tain an amount of the solute capable of combining with eight 
grams of oxygen. 

It is usually more convenient to prepare a solution of approx- 
imately normal concentration and then to determine the relation 
of its concentration to that of a normal solution by accurate 
anah'sis. 



61 

Normal Hydrochloric Acid. 

Thus to prepare a solution of hydrochloric acid of approxi- 
mately normal concentration and to determine its normality, pro- 
ceed as follows : 

Our concentrated hydrochloric acid has a specific gravity of 
1.19 and contains 37.23 per cent, by weight of hydrogen chloride, 
therefore we have 

1.19 X V X .3723 = 36.4G 
V = 82.3 c.c. 

Take 82 or 83 c.c, of the concentrated acid and dilute to one 
liter. Mix thoroughly and fill a burette with the solution. Take 
two portions, each accurately measured, of approximately 10 c.c. 
each. Dilute with water to about 200 c.c. and add an excess of a 
solution of silver nitrate and a few drops of nitric acid. Digest 
and stir in a subdued light till the liquid has become clear and 
bright. Allow to stand in the dark. Prepare a Gooch crucible, 
dry at 170 degrees C. and weigh. Filter, wash with 1 per cent, 
nitric acid, dry at 170 degrees C. and weigh. 

Then we have: Normality = 100 X w/143.33, where w 
is the grams of silver chloride obtained from 10 c.c. of the solu- 
tion. 

In preparing "/^ or "/,o acid proceed in the same way, start- 
ing with one-half or one-tenth of the quantity of concentrated 
hydrochloric acid. 

Normal Sulphuric Acid. 

Proceed in a similar manner to that employed in the case of 
hydrochloric, noting that concentrated sulphuric acid has a spe- 
cific gravity of 1.8-1 and contains 9,5.6 per cent. H, SO4 by weight. 

It is standardized by precipitating an accurately meas- 
ured volume (approximately 10 c.c.) with barium chloride 
and weighing the barium sulphate so obtained in a Gooch 
crucible. Normality = 100 X w/233.4, where w is the weight 
of barium sulphate obtained from 10 c.c. of the solution. 

Normal Potassium Hydroxide. 

Assume that pure stick potassium hydroxide of the laboratory 
contains 10 per cent, inert foreign matter, chiefly water. Take 
such a weight as will give 56 grams KOH, dissolve in water and 
dilute to 1 liter. Mix thoroughly. 



62 

Fill two burettes, one with an acid of known normality, the 
other with the solution just prepared. Take the initial readings 
and draw into a beaker or Erlenmeyer flask from 10 to 15 c.c. 
of one of the solutions, add one or two drops of methyl orange 
(or other suitable indicator) and run in the other solution till a 
permanent color change results. Then alternately add each of 
the solutions till the color change is produced by the least possible 
quantity (a fraction of a drop) of the more dilute solution. Avoid 
splashing and rinse the sides of the vessel before the final adjust- 
ment. 

Calculate the normality of the solution from the mean of at 
least five trials. 

CHOICE OF AN INDICATOR. 

Methyl Orange. 

Dissolve 0.022 grams in 100 c.c. water, add O.GT c.c. "Ao HCl 
and filter after standing some time. 

Uses. — In titrating strong acids (HCl, HNO,,. H.^SO^), 
H3PO4 reacts neutral wdien Na H. PC)^ has been formed ; H.SO3 
when Na HSO;, has been formed. In titrating all inorganic bases 
with strong acids. 

Lacmoid. 

Dissolve ".2 gram in 100 c.c. alcohol. 

Uses. — In titrating strong acids and bases ; also ammonia. 

Litmus. 

Of such a concentration that three drops of the solution 
impart a distinct color to 50 c.c. water. 

Uses. — In titrating strong acids and bases and ammonia. 

Phenol-Phthalein. 

Dissolve 1 gram in 100 c.c. 80 per cent, alcohol. 

UsES.-^In titrating acids and strong bases. Not for ammonia. 
H., PO^ is neutral when Na^ HPO^ has been formed ; H. CO3 
when Na HCO., has been formed. 

This is the most sensitive indicator for the titration of acids. 



OCT 18 1912 



